I do agree with carrots' analysis, only I expect this guy to have a wider range than he might normally due to him showing down QQ last hand and splitting the pot with 55, meaning he's possibly slightly tilted, plus he'll maybe feel more confident he's getting respect thanks to his QQ showdown.

At 10nl, I see people bluff with all sorts of shit. I think at 100nl I would imagine people are bluffing sensibly, that is when they feel villain's range is weighted heavily towards thin value hands that fold to aggression, or bluffs etc.

At 10nl, I expect a 3bet bluff pre to cbet flop and then check turn if called, thinking he's getting value towned by top pair. When turn goes c/c and we check river, now he feels confident we don't have a king.

I do see nutty hands make large overbets like this on the river at 10nl, but I also see a lot of bluffy spew too. Throw in the dynamic of the last hand, and this is why I'm not folding this spot. I don't think villain is as tight as he would be if he'd been quiet for five or six hands.