It happens because these technologies solve real problem for some subset of their users. Usually when people are saying that technology has become too complicated, it's because they happen to be looking from a perspective where the problems that the technology solves are invisible to them. That doesn't mean that the problem isn't important - it just means the problem isn't important for them. The easiest way to motivate this is to imagine the kinds of problems that need solving at large companies with thousands of employees. They look vastly different than the problems of someone like me working on a side project by myself.
e.g., TypeScript might not be useful for some single-person teams of developers. It's quite useful for teams of around 5, and it's unthinkable to work without it in teams of 100+. Does this mean that the single-developer team is wrong?
(I'd actually say the same thing about React. If you're a one-man team, go ahead, do whatever you want. But if you're working with 100 other engineers, god help you if you're all directly manipulating the DOM with vanilla JS.)
Most "complex" technology is solving many problems for many different smallish subsets of its users at the same time. To the average bystander, it can look like the technology has gained huge amounts of unnecessary complexity, but it hasn't, not really - it's just complexity which isn't directly relevant to you.
(OK, and yes, some other technology is just needlessly stupid, but...)