Lets not forget that Jet2 also failed to make this route a success despite high loads particularly in the morning
Not sure that it was that Jet2 couldn't make it work, I believe that they could make more money sending the aeroplane to other destinations rather than LGW and back.
Jet2 transferred the slots to a NCL service when they pulled the MAN route, at that time BA still operated the MAN service but had pulled the NCL route, leaving it unserved. This service was pulled some time later in favour again of sending the aeroplane to destinations where it made more revenue.