It's funny you say this, because I saw tweets decrying how crowded it was. Bad luck on their part in terms of crowd patterns, I'm guessing.
Crowd patterns resort wide were weird 9/4-9/9. 9/5 and 9/6 were very dead during the day and very manageable during the event, with 9/6 of course being more crowded. The daytime parks were busier over the weekend, naturally, and the event was packed on 9/7. (9/8 was a fluke, I think, thanks to the monsoon.)
9/9, though, a Monday, was shockingly busy. Even ET had a 40 minute queue (actual ~20) with all three preshow lanes open and both loading stations.