How many of them made a lot of money chasing a literal fad -> foodie shots?

My great idea is to make a blockchain version of HN and instead of karma you get HNCoin, just need a 100 million dollars and a top-100 userbase...

You are mistaken, these aren't fads but buzzwords. Web 2.0 is the web of API, NoSQL existed well before the term was invented and microservices are a valid software architecture since it's not a question of size but an organizational concern. Even "severless" is just the good old worker queue system. And yes, buzzwords come and go but nothing behind these are fads.