Does anyone have any technical insights as to what happened here? Was it related to Google's new account deletion policy or something totally separate?
You'll never get an answer to this because answer == admission.
If you want a guess, it probably was related to pruning old accounts/old files.
Yeah, the timing is suspicious. Wonder if someone just fat-fingered a command.
I wonder if there is any correlation to the files deleted and the user accounts that were pruned--basically the file was deleted because you shared it with a user account that was pruned