The lack of Disney character importance in Chain of Memories wasn't Nomura's ego. Square Enix wanted Nomura to make a port of the original Kingdom Hearts for the GameBoy Advance, because back in those days the popular thing to do was to make sure a game could be accessible both at home and on the go. But Nomura didn't like the idea of wasting his time just remaking a game (ironic, I know) and instead decided to go above and beyond and make it a sequel with an original story. But because the idea wasn't meant for it to be a sequel right from the get-go, the mechanisms for talking with Disney about which movies they could work with weren't set up. And, as Nomura has stated, working with Disney in terms of getting access to their movies has been a constant "teeth-pulling process" over the years, so he probably just didn't want to deal with them just for the sake a handheld game that would only act as an interim title.Nomura's also the one that turned down the idea of Donald being the protagonist & insisted on making his own character. There's also a stark contrast in the writing of KH1 to the rest of the series. Disney characters mattered in KH1, the Disney villains drove the plot. From CoM onwards, the Disney characters are relegated more & more to filler while the number of spotlight-stealing OCs reach into the dozens. It's like he played it safe for his 1st game but once he found success, his ego took over.