You don't need years of trials. One thing that people forget is that types are a parallel ecosystem more times than not i.e. DefinitelyTyped. So you do not have that lock-step that is praised. So imagine wanting to use a brand new webextension api - stop, add it to types. Want to upgrade a dependency - stop, the types are not working/incorrect/incomplete e.g. https://github.com/DefinitelyTyped/DefinitelyTyped/issues/17...

AFAICS the Typescript types ecosystem is bigger simply because Typescript has been advertised to devs coming from a background of a statically typed lang, and they cannot imagine not using types, thus they drown in them.

Flow on the other hand appeals to those that want types primarily in their own codebase, and come from inferred/dynamically typed langs, where you gradually add static types starting with key sensitive parts in your codebase e.g. Erlang http://learnyousomeerlang.com/types-or-lack-thereof