Linux focused companies like Microsoft
my sides
Being a contributor to an open-source project is not the same as actually owning a "commercial" product. They can voice opinions in the mailing lists, but they don't have direct influence. Sure, some maintainers work for those companies, but I would say that's hardly the same. It's sponsorship, and it's welcome pretty much no matter where it comes from in my view.
If those companies disappeared overnight, Linux would be fine. Development would be a lot slower, sure, but it wouldn't implode and instantly become worthless like macOS or Windows
Man, there's some lore behind Nvidia support in Linux. Short of it: Nvidia are assholes, they pretty much could give Linux users an on-par experience to Windows, but don't want to. Things have been generally improving in the last 5 years or so I would say though. CUDA and PCI Passthrough also usually work, so getting a cheap Intel Arc to draw your DE and using your Nvidia for heavy lifting is a relatively cheap and 'drop-in' fix to your workflow.