If you were on USAirways, you were most likely on a Regional Jet from Phoenix, as that is the only destination that US flies to from MRY. Checking the schedule, you were most likely coming in around 10 pm, unless the flight was late. The closest airport would have been SJC, but US does not fly RJs into SJC and indeed may not have had the equipment available. I also do not see any US RJs flying into SFO. That would only leave OAK, and I think it is a tossup as to which airport is closer to MRY, OAK or FAT.

You don't say, but I'm guessing you were bussed to MRY. It could be that it was quicker for the airline to get buses available out of FAT than OAK. The other issue that we don't know about is gate availability. Many aircraft park overnight at the gate, and it could have been that there were no US gates available at SJC, OAK, or SFO that late at night.