KJo flop trips with resistance

[DyessMan89]

Reads: None that were real strong, but Nik has limped with a lot of hands. More than most players at the table.

7 players, blinds 7/15.

Game #790748373: Texas Hold'em No Limit (7/15) - 2005/08/05 - 22:39:04 (UK)
Table "STT1 902375 - 1" Seat 4 is the button.
Seat 1: Masester (985 in chips)
Seat 3: caliman (810 in chips)
Seat 4: Monty23 (940 in chips)
Seat 5: MrVegas (4535 in chips)
Seat 8: Niknaknoo (865 in chips)
Seat 9: Psycom (895 in chips)
Seat 10: Fatcow (970 in chips)
MrVegas: posts small blind 7
Niknaknoo: posts big blind 15
----- HOLE CARDS -----
dealt to Monty23 [Jd Kc]
Psycom: calls 15
Fatcow: folds
Masester: folds
caliman: folds
Monty23: calls 15
MrVegas: folds
Niknaknoo: checks
----- FLOP ----- [5d Kh Kd]
Niknaknoo: checks
Psycom: bets 150
Monty23: calls 150
Niknaknoo: raises to 850 and is all-in
Psycom: raises to 880 and is all-in
Monty23: calls 730

Now, there was a similar thread on this before, and Im going against my own advise, but I felt this scenario was different. I felt that the UTG was overplaying a lower King, although SB was still a mystery. Any comments?