Okay so pre is unexciting.

I could raise flop or turn since my hand has equity and doesn't mind getting folds but I prefer calling. (I'm open to hear thoughts on this but I'd mostly prefer to hear thoughts on villain's river line.)

River: (He shows up with KcQsTd9d in case it doesnt show in HH)

I can think of 3 reasons for villains line.

1) I have a lot of KQ and he folds me off a split. I don't think this is true as I have a bunch of incentive to jam most/all KQ on the turn. Even if I have some KQ its an unbelievably expensive play to bluff KQ to get me to fold a split sometimes when hes getting scooped by a flush sometimes too. I'd need A LOT of KQ to justify this play and I don't think I do).

2) I'm so flush deficient that I'm forced to call a bunch of non-flush hands making his shove a good value bet (this seems not particularly likely, since paired with 1 it means I'm calling river here with lots of 2p or non nut straights...)

3) Due to range on range composition or w/e I'm forced to fold a lot of flushes making his hand actually a good bluff (this seems unlikely to me given how high the EV of checking with a straight must be). This would only occur when he has nowhere near enough bluffs and even then there seems to be a reasonable likelihood checking is still superior.

4) He just made a mistake.

During my NL career I'd have looked at a hand like this and thought "lol idiot" or "he made a mistake/is tilting/misread hand etc)

That being said, villain is IMRU_BEAN who I hear is extremely good and from what I've seen to this point is good. Is there a lot of merit to this play or is it simply a mistake made by a good player?