There is strategic coherence.
When you have a closed league, every club becomes more valuable because they all have a guaranteed stream of income for the foreseeable future. It makes it easier for teams and the league to negotiate all kinds of big commercial deals. In addition, the closed nature of the league creates scarcity, inflating club value.
Once you look at the player dynamics, you can dump transfer fees, a major source of waste. That value gets split amongst grand and players. and then the closed nature of the league allows you to control employment access, enabling drafts. This then allows you to use drafts as an equalising mechanism. Finally, you can impose a salary cap because of these closed and equalising dynamics.
This is why the hybrid super league model didn’t make sense. They needed to do a complete breakaway to mimic this model