The reality is there are spare long haul aircraft sitting around during most of the year to plug the holes when unexpected maintenance crops up. However, the international side of the airline makes nearly all its profit during the Christmas holiday break so they push all the aircraft into service, as you would expect. This means disruptions are harder to handle and you need more creative solutions and you’ll piss off more passengers but that is what running an airline is all about.
I would have thought that NOT pissing off your passengers is what running an airline is all about, especially at a time you are charging peak fares and with little alternatives to offer in recompense.
Happy now? End result is still pissed off passengers ie customers. Never good for business.