Perhaps they're farming accounts? As in, the owner creates a whole bunch of accounts and has them build up a generic history. Then when the owner "deploys" some of them to pump up a specific issue. I don't know why they remove the posts, but perhaps it's a way of "recycling" an account by cleaning up the dirty work it did and throwing it back into the pool of available accounts?
Come to think of it, I bet the original creator is selling these accounts to someone else who is weaponizing them. Or the creator is renting them: build up a supply, rent them out for a purpose, then scrub them and recycle. Work From Home! Make Money Fast! This is one part of why the internet has gone to hell.
I don't have an explanation for why they'd delete the accounts.