The tolerances(spaces between moving parts) in the AK are loose. There’s lots of room for gunk and dirt to get in there and the gun will still fire and cycle when the trigger is pulled. With loose tolerances, failure to properly clean and lube the weapon won’t hinder it from firing like the M-16 from the Vietnam era.
In addition the AK uses a gas piston technology rather than direct impingement. Both systems use the gas from the recently fired round to load the next round. With the AK the gas is directed to a piston rather than directly at the bolt carrier. This keeps the bolt cleaner and results in less jams. However, it creates additional movement not present in the direct method and therefore sacrifices accuracy.