Corporations are not only about money right now, but also about the assurance of money coming in in the future.
This means bargains can be made if both profit from it. Universal has the rights to some very popular Marvel characters in FL, but nowhere else. Nor does Universal has access to the full Marvel Cinematic Universe versions of those Marvel characters (just the comic book versions, which have been updated to be closer to the MCU than the ones in the past).
Both companies are making money from Marvel characters in FL, since it is a license.
Both companies can also make money from Marvel characters in FL if they share the property and everything is updated to MCU.
Imagine both a Marvel Universal Island of Adventure and a Disney Marvel Land. Imagine if Universal was allowed to re-create their MUIoA in California and internationally as long a Disney could create a Marvel Land in FL and start being able to use the "Marvel" name in the U.S. And everyone's version of Marvel characters will be updated to the MCU.
Will this happen? Probably not. But, there is an alternative to fighting over exclusivity: Sharing. And sharing the money it'll make.