A good example is React. Facebook's interest is that React be performant (website performance is correlated with time spent on said website), reliable (also correlated to time spent), quick to build on (features ship faster) and popular (helps new recruits hit the ground running). That's fairly well aligned with what developers outside of Facebook want too.
Sure, since Facebook's server is written in Hack it means we'll never get a truly full-stack React, and instead we'll need third parties for the back-end (Next.js, Tanstack Start, etc). But Facebook building react also means it will always be someone's job to make sure this Framework works well in codebases with millions of modules.
This is all independent of any shitty practices with their other software. And this has been for decades at this point.