He mostly just got lucky. If it's a really important tourney to you, and very early, you can sit back for a longer time before you "pounce" on him. You'd rather have a "made hand", of a mid-pocket pair or higher, but you can't always be sure that will come in time. But it sounded like this was happening to you right at the start of the tourney, and in that case you have many rounds you can sit and wait for even a better hand than AQ.
Another factor you need to consider, is that many times these type players will stop going allin once they have doubled up a couple times. If he literally keeps shoving EVERY hand, no matter what, then you know you will be ahead with AQ. However, you also know that if you wait a few more and get a mid-pair or better, then you will be even better off.
Plus, if it's a tourney that is important to you, then you might also NOT want to call his all in, especially if you might be only ahead 55%-45% or even 60%-40%. Because that 40-45% you would lose, even though in the long run it is a "good play", still does not mean it's the right play for THIS situation at the moment.