the route only operated as a gap-filler until something better came long?
This winter Krakow and Billund were dropped from the Malta base. Both are returning next summer. This meant there was a few long gaps for Malta based aircraft.
When the route was first announced both flights between BHX - Malta were operated by the Malta based aircraft but when Ryanair announced the closure of their Marseille base the Malta flight times had to be changed to accommodate Marseille twice weekly. Thats why one of the flights is operated by a BHX aircraft.