A lot of companies also contributed to Linux, but that's not the issue.
The concern comes from having a *small* number of companies with a notoriously aggressive behavior controlling a project.
Google is especially known for using products as weapons against competitors and drop them suddenly after a while.
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.
As for Perl, I just look at it as a stepping stone for more modern scripting languages.