vote farming of Steemit Inc faucet accounts and/or compromised accounts
This is a common tactic of vote farming operations. The Steemit.com account creation had previously been a very easy actor vector to create thousands accounts that would proceed to circular vote each other to amass Steem Power for further exploitation. If I recall in this case, the accounts voting have had their posting key compromised.

Ok, so zombie sock-puppet accounts. Can't you just pull all their newb delegated steem (15 steem-power from @steem)?

Thank you for explaining this. I've seen the term "vote farming/comment farming" a few times and I had no idea what it was referring to.