This post is how I would play as villain and should illuminate why I think his play was bad:

Since I am in position on the 3 bettor, I would flat call with AK here because it disguises the strength of my hand, keeping in hands that I have dominated, and the only hands that call a 4bet shove have me beat. If I get check-raised on the flop it is an easy fold and I have minimized my losses and I live to fight another day. If I get led into I am just calling for pot control, and if the 3 bettor check-calls my cbet, I am checking back on this turn (it merges my range really well and keeps the pot from getting too crazy in the event I am beat). If I get led into on the turn I have a decision to make because this line polarizes his range to nuts or nothing. Given that he most likely does not 3bet with 66 that often in this spot, I am only worried about the 3 combinations of QQ, and therefore, I'm going to shove over the top of a turn bet most of the time. The river does not really change much because by following these lines on the flop and turn, he rarely is going to have 10s and you don't need to worry about AJ for broadway. If he checks, ill check back for showdown value, and if he bets im snapping him off because he's usually got air or he tried to trap me with QQ on the flop/turn and felt he needed to get value on the river (another reason to keep play pot control).

Hopefully this illustrates why POSITION (not cards) is the MOST important thing in playing profitable NLHE.