Making Willem Dafoe's Green Goblin the main villain of Spider-Man movie, but his role was almost quite different.
Maguire, Garfield, and Holland's Spider-Men teaming up did.
Despite having an assortment of Spider-Man villains from past movies brought into No Way Home, none of them are inherently evil within the film and the three Spider-Men give them all a path to redemption. Norman Osborn is more of a unique case among the villains, due to having a distinct dissociation between his identities as Norman Osborne and as Green Goblin. Unlike Norman, the Goblin is a genuinely evil, murderous sociopath, and having him in the movie made the situation far more dangerous for all involved.
The Green Goblin persona taking over Norman's mind and killing Peter's Aunt May (Marisa Tomei) worked to establish him as arguably the most violent of the five villains. This gave Spider-Man: No Way Home a very personal villain conflict with Tom Holland's Spider-Man against the Green Goblin, despite him not having a previous connection to the range of villains. Compared to the movie's other villains, the stakes were far higher with Tom Holland's Spider-Man having to battle with his vengeful urges that brought him close to killing Norman.
While Doc Ock (Alfred Molina), the Sandman (Thomas Haden Church), the Lizard (Rhys Ifans), and Electro (Jamie Foxx) all had to be stopped and sent home, they weren't as directly murderous as the Green Goblin. Norman Osborne's presence also brought the shared centrality of all three Spider-Men's mantra of "With great power comes great responsibility" into Spidey's adventures in the MCU for the first time. Tobey Maguire and Andrew Garfield's Spider-Man iterations recounted their Uncle Ben stories to help Peter Parker see that Aunt May did not die in vain. For Holland's "Peter #1" to understand the victimhood Norman himself had fallen under, No Way Home needed a centralized antagonist, and there was no better candidate for that than the Green Goblin himself.
No Way Home's gimmick of the three Spider-Men uniting against villains from other universes made it into the a huge theatrical hit. Even the mightiest of heroes are only as strong as the villains they overcome. Spider-Man: No Way Home ed that very well in making Willem Dafoe's iconically sinister Green Goblin its main villain in the three Peter Parkers' quest to save him from the monster in his mind.
