Why slowplaying monsters in Limit can bite you in the ass

Paradise Poker 5/10 Hold'em (4 handed) FTR converter on zerodivide.cx

Preflop: BB has Q, T.
UTG calls, Button calls with K, K, SB completes, BB checks.

Flop: (4 SB) 6, 2, 3 (4 players)
SB checks, BB checks, UTG checks, Button bets, SB folds, BB calls, UTG folds.

Turn: (3 BB) 8 (2 players)
BB checks, Button bets, BB raises, Button calls.

River: (7 BB) 9 (2 players)
BB bets, Button raises, BB 3-bets, Button calls.

Final Pot: 13 BB

There's a couple things I don't understand here. First of all the button's limp with kings - baffling. Second, the BB's check-raise on the turn with just a draw. What's the point? After two bets from the button, and with a pretty sizeable pot going, fold equity has to be very low. BB has shown no prior strength in the hand and the board is scattershot.

BB can vary from LAGG to TAGG. Button can vary from Loose-Passive to LAGG.

I can tell you BB's take on this hand - I can't tell you Button's. BB called the flop with the intent of raising the turn if there was no A K or J. Button was playing exactly the same way with hands like AK, AQ, 77 - he has folded turn raises previously. The turn raise actually became a semi-bluff thinking Button might fold and that he had 9-15 outs if it was called.

I'm not saying it was a great or even a good play by the BB. I am saying it was a horrible play by the Button.