They can contribute without having any special status. Rust already has a robust RFC process and good technical leadership. My worry is that these things weaken and rust very gradually becomes your typical corporate software product where more and more independent features are just bolted on without care to any larger vision. That won’t happen if FB, etc keep contributing as ordinary contributors. But it could happen if they’re elevated to a position of leadership.
Note that the Foundation doesn't have any impact on the RFC process or the project's structure or governance, so while that worry may exist, this announcement isn't a path towards doing that.
As for C, sure, AT&T is so much better than FAANG. C++ was also heavyly corporate. Python won over Ruby because of FAANG support (I personally like Ruby more, but as it's not supported by big companies, it remained behind in deep learning for example). Also NVIDIA has great Python support, which is really important for high performance software development.
As for Perl, I just look at it as a stepping stone for more modern scripting languages.
Sure tying Rust development cycle to Azure+VS code, AWS or GCP would be quite bad (run rust-analyzer on Azure for example). At least Facebook doesn't have this kind of infrastructure yet.
I wouldn’t say so. A language like Haskell is successful, even if their motto is “avoid success at all costs.” Books have been written about the language, and the ecosystem and community are thriving. Even still, few corporate sponsors exist.