Well,
Even if he didn't fit, they would squeeze him and 5 other villains into a movie just because.
This is something I really don't get with Hollywood. This isn't a about Spiderman but just comic book movies in general. For whatever reason they feel jamming 3,4,5 villains into a movie is a good idea. It always feel like they wanna blow their load with so many and it makes each of them seem kind of worthless.
An example would be Spiderman 3 which pretty much everyone hated plus the acting was aids, but they threw in Green Goblin, Sandman, and Venom when just one would be enough and you could use the two hours to develop suspense and story.