If the flop misses, it's checked to you in a multiway pot, and the pot is small, take the free card. If the turn misses you and someone bets into you, the pot is now doubly small, it's an easy fold. Fit or fold is not insane, it's just that Miller is stressing to take the pot size into account. 3rd pair beats ace high, and in a small pot, it's not paying you enough to chase.

If you want find out more on playing AK, search it up. I punched in AKo and pulled up 200+ posts in the last month alone.

Here's one from searching "AK misses" (use quotes for exact match).