It's very difficult to argue that easyJet should not have set up a package holidays brand whether Jet2 were doing it or not.
Large transport companies have been using this device to sell more bums on seats for years. Want a holiday to the USA ? Any of the large airlines can book you into hotels and sell you car hire - as long as you buy flights with them. Similiar thing with ferry companies or even coach companies. It moves the customer from a neutral travel agent who gets either commission or fees and is relatively agnostic between airlines to an in house own brand travel agent that sells flights on only one airline. If some punters are too lazy or lack confidence or knowledge to do their research into what's available from other suppliers why shouldn't easy take advantage ?