Remember how people said that from millenials onwards every generation will be skilled in tech? It so happens that gen-z actually ranks lower in advanced tech skills. Gen-Z learned to use tech, but not to understand it as much as those of us who experienced the early-to-mid internet and computers.
As such there's a large amount of people who don't know or understand the pros of decentralized platforms like Mastodon. And of course, there's also the artists who need to follow the masses because they make a living out of it.
I'm oversimplifying things a lot, but if you grew up discovering the internet through your parents' ipad, there's a higher chance that the corporate internet has a much strong impact / incentive for you.