Presumably the Welsh regions need money and if CVC are investing they'll be looking at ways to increase the revenue of Welsh rugby.
A combined league seems like it almost certainly achieves that goal for the regions.
However, CVC also have to increase revenue of the English game, and I feel like this would be a short term solution to that.
It would feel new and different. They'll be able to organise some good sponsorship for 2-3 years, maybe a little longer.
Suddenly, their goals are met.
But what after that??
There's already a feeling that it's difficult to attract new audiences to rugby, so while additional sponsorship and TV coverage may make a difference for a couple of years, if it tails off after the novelty wears off, then we're all left with a league that no one really wants, and no long term financial benefit to it