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
I think some developers have had a grudge with Javascript since the dawn of time and just cannot move past it. They'd rather move mountains than try to adapt to the environment.
Definitelytyped is frustrating; sometimes they have the type definitions sometimes not. Often the definitions are out of date and new ones are not available. Sometimes I feel that it's better not to use it at all... That way I don't have to think about it.
You don't have to add types to start using a new library or web extension. At most you have to add 'declare var foo: any;' or cast a builtin to any if the type declaration doesn't have the property you need. Typesript always lets you use the any type as an escape hatch if you don't have types.
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