Acquisitions are notoriously difficult to do successfully, although managers always try to tell us how well they are doing. It's very easy to destroy value rather than create it, so to proceed with an acquisition, the purchaser must have a very clear strategy, which is supported by the acquisition.
In the case of EZY buying GB, they were buying slots and routes at Gatwick, not the aircraft.
I tend to agree that EZY would be more likely to buy Monarch for its routes and slots at LGW, LTN and MCR than for its fleet. A purchase of Jet2 would give slots at STN, NCL, GLA & BHX that EZY don't want, or don't need to buy. They certainly don't want the Jet2 fleet.