That would not make much sense operationally. The LGW-LIS-LGW crew operated a two sector day. Therefore they have a lot of slack in the FDP allowed and there was very little chance of that crew exceeding their hours as it was just a two sector day.
Spare aircraft and calling in an ENTIRE new crew and a spare jet to operate a moderate delay would not be an efficient use of resources. A spare crew and jet are send on rescue flights where there is a risk of people be stuck/flights cancelled. There was very little chance of this occurring on this flight therefore the airline would have protected its standby coverage in case it really hit the fan on another flint and quite rightly so.
If the airport standby jet and crew were sent to LIS and another flight went AOG or crew out of hours due to delays then that fight would need to be cancelled as the standby is covering a delayed LIS flight, you have up to 180 adults plus babies stuck for the night. It could be that the airport standby jet/crew could have easily rescued said flight but because it was covering a moderate delay, then they're all stuck for the night. I'd hate to be the one who has to tell passengers that they could have been home that night, but instead the rescue jet was sent to LIS to cover what would be a slight delay in comparison to their's.
Getting people where they need to be is always the priority and delays will be accepted in order to protect the program. That may sound cynical but you need to pragmatic. A four hour delay vs. 180 people stuck and 180 hotel nights potentially then it really is a no brainer not to mention the human side of it all.
If you are unhappy with the result then my advice would be to raise it with the CAA and get them to look over it.