It wasn't anything to with Jet2. Besides the principal is completely different to what Jet2 are doing these days. It's dynamic packaging pure and simple. It is simply a way of making revenue by making it easier to book flights and accommodation in one transaction... Making it seamless if you like.
This type of relationship with 3rd party businesses is what the brand licensing case with Stelios was all about. Jet2 holidays has become more like TCX and TOM these days than Easyjet Holidays.