I've never flown for Ryanair but I have found myself being presented with an aircraft which had already been pre-fuelled for a much longer sector and that is going to mean that the aircraft will be over MLW at the new destination. It was not possible to de-fuel the aircraft nor was the aircraft fitted with a fuel dump facility.
So, the only solution was to get airborne and burn off fuel as quickly as possible (for example, keeping the airframe de-ice on for the entire flight and holding with the gear down at the other end) to get down to MLW.
It's a terrible waste of fuel but the operations department have probably worked out that it is the cheapest option available.