> But then LLVM showed up and showed it is no longer imperative to have a viral license

I am not sure I remember everything right, but as far as I remember Apple originally maintained a fork of gcc for its objective-c language and didn't provide clean patches upstream, instead it threw its weight behind LLVM the moment it became even remotely viable so it could avoid the issue entirely.

Also gcc didn't provide APIs for IDE integration early on, causing significant issues with attempts to implement features like refactoring support on top of it. People had the choice of either using llvm, half ass it with ctags or stick with plain text search and replace like RMS intended.