Using the same philosophy Prestwick 5 years ago should have been the busiest airport in Scotland as its figures for Stansted were the highest
I don't follow your logic at all. The suggestion that Malaga etc could work from LDY is based on the passenger pool from Northern Ireland to these places and LDY's expected share of that were a route available. It's not based on LDY's figures.
For example, Tenerife had a passenger pool of 57K in 2009, Malaga had a pool of 166K. The logical conclusion all things being equal is that if the route with lower demand can be made work then a route with higher demand should work.
Eindhoven is a bit problematic. It is Ryanair's version of Amsterdam, about the same distance from Amsterdam as Belfast City airport is from Derry. Amsterdam could certainly work following the logic of the previous paragraph but whether Eindhoven would is a point for debate. Ryanair in their wisdom seem to think it an acceptable option for Amsterdam.