Yeah, I’d agree. While not necessarily the last leg of the entire trip (who’s going to fly the plane out from DSM?), almost certainly either:

1) last leg of the day, and they were going to time out.
2) UA needed them into DSM no later than 10:17pm, so they could get the minimum rest and fly DSM-IAH at 6:17am the next day.

Delaying by 30 mins means the flight the next day is late, ..... another whole day’s schedule.

EDIT: plane went back to IAH so not sure if the same crew flew.... I thought rest minimum was 10 hrs but maybe it’s 8