Weird river spot with AK

[OwChS]

The chk-raise is to protect a weaker hand. Why would he chk-raise so strong on the river? Why not lead out 3/4 - Pot with a boat/trips? If he had AK he would've most likely C-bet the flop or lead out on the turn. His play makes no sense. He chks the flop & the turn w/ a big hand but instead of leading on the river he chk raises, HUGE. His humongous chk-raise on the river defeats the purpose of even checking on the river to begin with. He chks hoping you'll bet so he can chk-raise for value, not chk-raise to push you out of the pot.

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