Why technologies go out of trend?

How to distinguish over-hyped technologies (which gonna die) from innovative technologies which gonna stay?

Yes, I know:

it is better to choose stabile technologies over trends
it is better to choose tools you know over trends
it is better to use tool appropriate for the task

But if the technology is popular (trendy) it means, there is big a community, which means easier to get support, a bigger number of community-driven libraries, a bigger number of vacancies, a bigger number of candidates to hire.

For example:

Do you remember CoffeeScript or facebook flow? On the other side, TypeScript is here to stay
Do you remember Adobe Flash (Flex)? Everybody use JS + HTML 5 now
Web components first was presented in 2011, yet doesn’t seem to be a mainstream technology. React was presented in 2015 and now it is everywhere (too much of it)