If you read the comments that preceded yours in responding to my question, you'll see that there are perfectly apolitical reasons for them to have done this move; they wanted a scale-out less DBA-controlled database, and at the time there wasn't a built-in Postgres way to do that.

Also, knowing how to scale DB X and not knowing how to scale DB Y often means scaling DB Y is a science project.

I feel bad for baiting people into psychoanalyzing Etsy's team.