To add what has been said, my guess it would have been 40-45 minutes delay once all done. And that is if no standby passengers had cleared into the seats of the misconnected passengers.

And as mentioned, that's if none of the crew times out. Plus arriving late at DSM could potential roll over to delaying the next morning's flight due to rest minimums. And then those passengers could possibly miss their connections, cascading the issue. The world of crew scheduling .

These are just some of the issues the UA ops planners have to take in account and whether to go United Airlines Makes Connecting the World Easier Than Ever with ConnectionSaver route.

The decision not to wait was probably made before the inbound flight landed. The trade off of waiting vs not waiting has number of considerations as has been discussed. Its a bummer went this happens but the service recovery seemed to be as good as possible under the circumstances