That's a nice meme from LinkedIn but I'm sure there a few other reasons including a better paycheck, flexibility, or even benefits.
At many, many companies, your manager directly decides or at least influences all three of these, so if you quit due to them, you're also quitting because of your manager.
They also rarely have much influence over work flexibility or benefits.
I'm usually very up-front with my reports on this. I make it very clear that I cannot compete with other companies on an immediate short-term compensation bump, so if they prioritize "money now" over everything else, then they should go out and interview.
However in the four years that I was a manager at my previous company, nobody on my team ever took me up on the advice to switch companies to get more money faster.
Did you believe you could deliver better long term compensation? This phrasing suggests that, it's a clever way to suggest something without promising it.
Usually, but not always. Of course it's impossible to predict 4+ years into the future, because so many factors can come into play on that time scale.