LGW is fast becoming slot restricted at peak times, leaving LGW at one runway maintains that and therefore suits easyJet current monopoly position, opening a 3rd or 4th runway at LHR would allow easyJet to move some operations there whilst still maintaining a sizeable LGW operation.
This statement has got nothing to do with lowering prices or improving competition, but is all about easyJets commercial needs, perfectly understandable