I genuinely don't 100% get it.
In general, they want higher salaries (like you mentioned), but there also seems to be a clear disdain for most of the portuguese cultural heritage, to be honest. This might be an ecochamber (I'd put money on it being the case) but most people "around me" who are in "the tech world" are pretty much diametrically opposed to most portuguese customs and culture. They don't really identify with the country, the history, the religion, the folklore, the politics, the sports...and if you add the income disparity to it, it makes sense that they want to leave.
If not for the will of my Significant Others throughout the years, I would have definitely left a looooong time ago.
(Man, I find it somewhat atrocious how much we like to tell the great stories of how we went and stole, raped, killed and enslaved during the time of the discoveries, all for our own pleasure (and that of our religion). I guess I can somewhat frame it in its time, but you will never hear me talk about our "great accomplishments" in that regard. I'm deeply ashamed of them, not proud.)
Is that really the general consensus over there? I'm trying to think of a way someone would rationalize decimating entire tribes over wood as a good thing but I'm coming up short.
Heck, we just had a president who thought Andrew Jackson was the best thing since sliced bread - and that guy is sort of the textbook definition of a cheerleader for genocide and slavery.
So, yes, people rationalize a whole lot of truly horrible stuff if it was "their" group doing the horrible stuff.
Edit: To be clear, that's not specifically about Americans or Portuguese. The "when we did it, it was good, but otherwise it's horrible" thing is a pretty universal trait.
I think this becomes more prevalent the poorer/less significant the country is today compared to their great past. It's the "good old times" phenomenon.
"Look at this cool palace we built and all the rare and exotic wood we used!"
"Where did you get the wood again?"
(See the general argument about decolonisation and re-contextualising within European countries, and fights over things like the Edward Colston statue)
It does not help that we have "Os Lusíadas" which is a literary wonder in terms of its form, but whose content is basically emphatically praising those times. I hate "Os Lusíadas" not due to its form, like many young people do, but due to its content and how it praises the story of how we went about being warmongers and rapists.
So while you say that people "rationalize", most people really haven't thought about it at all.
[1] We're one of those countries that are so small or have such an inferiority complex that we are obsessed with anything in the news or history of the world that involves us. We go crazy because Obama's dog is a "portuguese water dog", or because "Cristiano Ronaldo" is well-known, or because some character in a sitcom mentioned us. So knowing that we were once "great" or "responsible" for something usually fills us with never-ending pride. I can't get this mentality, and I very much despise it. I guess it just shows how disconnected I am. I love our people, and I think we're genuinely nice, polite and have decent work-ethic, as well as a country with reasonably beautiful landscape, a safe environment and nice weather (not for me, but for most people). However, that's about it. In other words, if a war broke out and I had to choose between leaving the country or fighting for it, I would definitely not fight for it, as it means very little to me. There are many things that mean much more to me than my country, and those I would be willing to fight for.
If you don't identify as Portugese, then most likely all these things will register as pretty decorations for your otherwise cosmopolitan life. If you do identify as Portugese, these things can register as an anchor preventing you from developing and exploring the possibilities of life.
That was certainly how I felt about the UK when I left in (3 decades ago).
For having access to good public transportation with regular frequency you need to live somewhere central in most of the big European cities. It might work out for you but locals are getting priced out because of these relatively rich Californian immigrants moving in and pricing out the locals. Now the locals need to move out to suburbs and use cars or not so frequent trains and buses.
Not that Portugal unique in its exploitative history, but this might speak to the mentality that the Portuguese "explorers" had when they went out into the world making their "great accomplishments".
If they were even all that different words to begin with. (Never actually learned Latin, just picked up words and phrases here and there.) In a mongrel language, originally Germanic but with massive direct and indirect Latin heritage, one can talk about someone's "daring exploits". Whose? Mainly, IME, those of people like Livingston, Stanley, Richard Burton (not the actor)... Explorers. "Exploits" as a(n English) noun does lead the mind more to thoughts of exploring than exploiting, doesn't it?
So go easy on your explorer-exploiters. The Portuguese ones were at least probably no worse, on average, than everyone else's.
("Verbing weirds language", they say, but it doesn't even need to -- language is plenty weird enough to begin with. All of them, probably. (OK, OK, except possibly Volapük and stuff.))
I left, now it is really hard to come back before retirement, due to the ways life drives us around.
It really feels like an ecochamber, or a generation thing maybe, because even with my regular visits I seldom meet people that think that way.
What I do meet, is the difference of working in Portugal, and how things work in central/nothern Europe.
Portugal is an amazing country with great food, people, and weather.
Kind of makes sense in that context. If youve got money the country is great. If you need to earn it it sucks.
You'll find similar problems in SE Asian countries. People want to escape their oppressive governments and lift their family out of crushing poverty and unaffordable living. People from North America and Europe see those countries as basically Disney World--just a world of beaches, forests, $1 meals and $100/month apartments, and they're more than happy to move in. Admittedly, I'm a person who also absolutely loved Vietnam (as a middle class white dude who has zero risk of ever running into political or social issues there and could afford anything I want easily), but I know countless Vietnamese people who have recently emigrated from there and hope they'll never have to return.
Most people moving into cheap countries are going there to live a lifestyle that in unachievable to them in their home countries.
I was thinking about Monaco, small town, but the actions are a high surveillance state with rigid rules, a monarchy. There simply are no poor people, but if there were, it would be seem as an oppressive autocrat (they have a congress/parlaiment, just like other autocrats do these days). But there aren't poor people, and its more like a perpetual gala.
They are so insulated from reality in their expat bubble that all the negatives locals see are actually positives to them.
I speak Portuguese (Brazilian) but most Portuguese people in the cities all seem to speak good English. Portugal is beautiful, has temperate weather and long coastline, really good clean food (sopa de legumes, leitão, sardinhas, etc), friendly people and easy access to the rest of the EU. And unlike traditionally aspirational places like Italy or Spain which are harder to move to unless you have the right lineage (for getting a passport), Portugal is within reach of middle class Americans.
That said, I was told that salaries aren't high for locals. For what it's worth, most younger people in Italy and Spain don't think their economic life is all that great either. The money seems to be in northern/central Europe, i.e. well, mostly Germany.
There are many places in the world where it's nice to visit but not to live, I would say, Portugal is the opposite. I could realistically see myself living there.