Coincidence? I think not.
An experienced, well-known force of nature joins up with a newer group that's getting all the attention right now. And then Namor joins the X-Men. This can't just be a coincidence.
Let's break it down. Namor the Sub-Mariner is a powerful remnant of a bygone age that began in the 1940s. So is Disney. Namor chooses allies based on circumstance. Over the years he's allied himself with the Hulk, the Fantastic Four, the Avengers, the Defenders, Wolverine, and now the X-Men all based on necessity. Namor integrated himself with these groups to improve his effectiveness. Disney is likewise responsible for numerous mergers. In the Disney's time of need, they allied themselves with Pixar to create something greater than either of them could have accomplished alone. That's the very spirit of the Avengers isnt it? Namor and the Avengers joined forces to defeat Attuma and Disney and Pixar teamed up to create Wall-E. Both titanic achievements for sure.
Both Disney and Namor started out in the water and moved out on to land. Namor is an Atlantean and Disney made "Steamboat Willie." Similar aquatic origins at the same time.
Namor and Disney are both characterized by iconic images involving revealing undergarments that expose your junk.