I heard unsubstantiated rumors that it was somehow antitrust-related. If they are selling off their device business (again), then it makes sense that the device drivers would not be part of AOSP...

> If they are selling off their device business

Android and Chrome are potentially going to be split from Google:

https://www.nytimes.com/2024/11/20/technology/google-search-... (https://archive.ph/egRL4)

Pixels are no longer the Android reference devices. An Android company ending up with the OS, Google Play and Google's OEM partners wouldn't need Pixels. That's a possible reason for the change. However, the simplest explanation is that they're continuing to take cost cutting to an extreme where it negatively impacts their long term revenue far more than the money it saves. A lot of Pixels were sold due to first class support for using other operating systems including it not voiding the warranty.