* Career advancement: At the time, Pattinson was a relatively unknown actor. The Twilight Saga offered him a chance to land a high-profile role in a popular franchise, which could significantly boost his career.
* Financial gain: The Twilight Saga became a massive success, generating billions of dollars in revenue. Pattinson's salary and subsequent earnings from the franchise were undoubtedly substantial.
* Exposure and fandom: The role made him a global celebrity. He gained millions of fans worldwide, particularly among teenage girls, which can be a huge advantage for an actor in terms of marketability and future opportunities.
* The story and character: While the books and films have been criticized by some, Pattinson himself has expressed that he found the story interesting and the character of Edward intriguing. He has spoken about being drawn to the "brooding and mysterious" aspects of the vampire character.
* Creative opportunity: He might have seen it as a chance to explore a genre he hadn't worked in before and possibly develop his acting skills in a different way.
Ultimately, Pattinson's decision was likely a combination of all of these factors. It's impossible to know for sure what his exact motivations were, but it's clear that the role of Edward Cullen had a significant impact on his career and life.