Motion activated AC? I've never seen that in a US Marriott property, especially a Fairfield Inn. Do you mean one of the standard box units that uses auto fan instead of constant?

Look, hotels are routinely booked to capacity, and most people do wake up in the mornings and take showers, brush their teeth, dry their hair, etc. I'm fairly certain that it wasn't an overuse of power. The fact that you had partial power in the room means it was a circuit outage.

It's a low-end hotel. Open up the window and deal with it.