Snap call.

Not sure what made him donk the flop into two except thinking his 99-JJ are good still and didn't want a C/B. He bets a bigger % of pot on flop thinking he's good and fears the raise on the turn by an 8 or bigger pair that called the flop, so he bets just over half on the turn, when you call again I think he thinks it's value town now on a hand trying to get to showdown, and bets the river a bigger % again. He thinks he is taking you to value town.