Overpair. WTBalls is he doing? 10/20

[Jman28]

If I raise flop, what hand is calling me that I beat? Even if JJ, AT and JT would've called a raise, they are drawing very slim OOP. (EDIT: meaning it's not THAT bad to give them free cards)

I'm really confused because I never have seen a line like the villain's here. Usually an overbet has meant significant strength in the games I've played. I thought T9 seemed likely.