But why didn't the Marvel nerds flock to Islands of Adventure? The Amazing Adventures of Spider-Man was the marquee attraction of the park for a decade.
The park had many issues, from the worst marketing I have seen on a project of that magnitude to a recession in early 2001 to 9/11 that really took any momentum from building out of the gate.
Ownership and management wasn't exactly great either.
No, that doesn't quite answer your question, but I'm not sure how many fans Marvel had in those early days. There was a reason UNI was able to swing such a sweetheart of a deal that goes on and on and on ... sorta like a refillable mug thread.