Seems likely that, in the first event, the then crew/maintenance, could safely postpone it. Given the peak time of year that would make sense.
Then the problem became one that, if developed during flight would have been OK (probable shut down) but not to start a flight with that problem.
TopBunk speaks from seat 0A and what the pax/crew/BA got was an aircraft home safely to main base, albeit at a price. The alternative price was to canx the flight for 24 hours. Again, at peak time of the year, whilst down the line and the follow on disruption to many other flights due a/c and crew out of time/place? The choice may well have been easier to decide.
The social media flare up of multiple canx flights at this time of the year is worse than a couple of delays, to yours and, possibly one or two more subsequent. Then back on track.
Lastly, the openess of the flight crew in detailing the problem is to be commended. So often in PPRuNe, we hear of the opposite.