all your assumptions are probably right. everyone may have their own motives. but for accounts that have been inactive for a long time, then woke up and deleted several posts that might be related to bounty campaigns or address information and social media accounts. I am more inclined that there is a possibility that the account will be sold or the account has changed hands. especially if there is a history of password changes, it will strengthen.
but still, each such case must have a different motive. there wouldn't be many people who cared about people deleting their own posts.