Comment by BirAdam

He didn't just "work on Windows."

GabeN was the lead developer on Windows 1, Windows 2, and Windows 3. When Windows 95 launched, he was a bit upset that no one was making games for Windows. He did a rough port of Doom to prove the viability. Around the same time Alex St. John, Craig Eisler, and Eric Engstrom were building DirectX, GabeN saw the potential, left to create Valve, and proceeded to try and making Windows gaming a great thing.

I can only imagine that he was heartbroken to see Windows go the way it did with Windows 8, 8.1, 10, and now 11.