> We've spoken with several dozen developers inside Apple, obviously not authorized to speak on behalf of the company, who feel that support for Nvidia's higher-end cards would be welcome, but disallowed quietly at higher levels of the company.

https://appleinsider.com/articles/19/01/18/apples-management...

Nvidia released drivers for macOS up to High Sierra indeed. After that, we don't know exactly what happened behind the scenes, but apparently Apple would not approve the Nvidia drivers for later macOS releases and switched completely to AMD GPUs.