A lot of things beat AA, AA isn't the best hand that once you're dealt it you automatically win. AA is the best paired hand, however paired hands are the second worst hand you can possibly have. We all have to learn that AA isn't some magically hand, its just two cards like every hand we're dealt. We shouldn't treat it as a silver bullet which will never lose and we shouldn't treat it as some cursed hand that will always get cracked. Remember your studies and play the hand is the most +EV way possible while acknowledging like every other hand there are hands after the flop that you will both lose to and beat but given our opponents range we can better say which side of the spectrum we lay on.