No guarantee, but what did the General Manager say when you raised the issue on the spot? Usually they will credit something to your room, comp a meal at the restaurant while you wait or somesuch.

You can, of course, send in a complaint and Marriott will toss you some points, but 99% of these things are best dealt with on the spot.

There are lots of reasons why rooms don't sometimes appear as they ought to. Note that your delay was 1 hour, not 2 hours as you arrived an hour before check-in.

Could be:
1. Earlier guest did not leave. Some states prohibit forcible evicting a guest, so it's just plain tough. In others even if the guest is physically tossed, that still takes time.

2. Room (or rooms) had damage and weren't useable.

3. Room was dirtier than usual and cleaning it took more time & effort than it ordinarily would.