WHBM - not teaching you to suck eggs, but.....
Load factor would only be one consideration. Yield would play, possibly, a higher part than pure load factor. No point cancelling yer most profitable flight in favour of one that was only just breaking even!
Route sensitivity also comes into it. New routes, or those that have been subject to recent heavy advertising, would be avoided if possible. Doesn't court favour with the pax & press if you advertise how wonderful the new route is, only to start cancelling it.
Pax re-accomodation plays a big part. It's easier to get pax from (say) LGW-NCL than from LGW-JER.
However, I think the summary for snapper is:-
No, flights wouldn't (normally) be cancelled for the reasons you give. Tech snags will always be treated with respect by engineering and ops and, if the snag is going to take time to fix, then cancellations will often happen. You were in a fortunate position to have an alternative flight fairly soon afterwards.