There were no flush or straight draws really, so he may have thought you had a 10 at best (if that), so why not call the smaller bets. Then he got lucky on the river.
That's the only problem with the lower limit tables, why we all get crappy calls that suck out. Sure, you may be betting 10xBB, but in reality people spend more on a pack of gum these days. So, to spend $1.05 to get to the river isn't much to see if his 9's held up. I think you may have the same problem I had which was not betting enough to knock him out after the flop. (this if from a rookie though). If this were a $2.00/$5.00, he probably would not have have seen a $65.00 bet by the turn, but for $.65, when he had $.40 in already, why not. The odds
may not be right, but he paid more for his extra cheese on his burger at McD's for lunch