I think windows has historical monopoly.

They bundled it with PC hw and the vast majority of apps only ever got published for windows, and this over decades (one would argue it’s still true).

The starting point for LLMs is very different. Who would publish today a software that only integrates with chatGPT? Only a small minority.

Thus I agree, I struggle to see how a monopoly can exist here. A GPU monopoly or duopoly though, perhaps.