Spider-Man is Marvel's flagship character, and his merchandise outsells every comic character combined, DC or Marvel. Sony was in trouble, and their movies would hurt the Spidey IP which makes so much money for Disney/Marvel. Fantastic Four and X-men are no way on that level. A deal like the Sony/Marvel wouldn't make sense for Fox/Marvel. What does Marvel financially gain off of it? By rebooting Spidey the right way through Civil War, they are essentially going to be able to sell tons more Spidey merch. That's not the same with FF4 or the X-men. Plus why should Fox get to benefit off of the MCU? Marvel spent time building the world and getting audiences invested, and if the FF4 and X-men want to be apart of it, I only want it if they're FULLY back at Marvel.