To those suggesting that UA should have accommodated the misconnects on other airlines, 65 passengers is a lot to accommodate. If UA booked every available seat on any other airline from SAN to CLE with a stop anywhere, it might have taken a day or two to clear the backlog. Delta, especially, flies very high load factors these days. Notwithstanding the financial cost to UA of hotels, this would have been disruptive to the passengers.
Also, it probably wasn't just passengers going to CLE that were affected. There may have been people flying SAN-DEN-XXX who also missed their connections. They would have to be accommodated as well.
Given what we know, I think UA acted reasonably to minimize disruption to passengers as a whole. An hour delay for a group of passengers is better than an overnight delay for another group. Of course, they could have avoided this by maintaining their planes properly, but that's a different issue.