Flow was (and still is) awesome as a concept, but its main problem was that it felt as a side-project, which was supported for internal Facebook cases, but not

Flow was (and still is) awesome as a concept, but its main problem was that it felt as a side-project, which was supported for internal Facebook cases, but not really for open-source. TypeScript (back then) was a simpler language, but had a lot more manpower, which resulted in faster bug-fixes and more coverage of libraries. If Flowtype had more resources from Facebook it could still be the dominating language