Your timeline doesn't make sense. Steam launched in 2003. Scully was forced out of Apple in 1993.
So, your right. But the still holds true, that seed was what was sown not to encourage games for the Mac.
If you watch the YT video they go in to depth that they attempted to port the game and was axed by apple.
Most valve games are 32bit macos binaries I assume for powerpc or Intel or something but they flat out refuse to run on modern ox