One other factor that's worth pointing out is brand value. We just heard from Bob Iger, himself, that Kevin Feige is going to take the helm for the X-men movie franchise once the merger is complete. He also made clear that there shouldn't be two branches of Marvel. They should be under the same roof. For Disney, who value their brand more than almost any other company, they have a huge incentive to make sure that the X-men brand is as valuable as possible. The best way to do that, at this point, is to make sure that X-men Dark Phoenix is the best movie it can be. Even though Disney isn't involved in making it, they have a vested interest in seeing it succeed. Unlike before, Fox isn't a competitor anymore and the X-men are part of their catalog. On top of that, Feige got his start on the first X-men movie. He's made clear that the franchise means a lot to him. For him, making Dark Phoenix great is the best way prepare the X-men for the MCU.