Yes i'll have a standby Crew for every flight and contingency and the punters can pay twice / three times as much for the ticket price.
Ops must have known the situation before the flight departed and should have made contingency plans, if possible, to minimise the delay and the overall cost to the airline.
It is not a case of having a standby crew for every flight but a case of having a standby crew at least at one of their bases to cover such eventualities.
However, if it is a case that a standby crew were already covering another flight, then its tough luck - these things happen, not pleasant but these things do happen.
I guess we do not know the full story.