He initially felt he could sell the rights and then ignore what was done with them (which isn't the case with Watchmen
, because he doesn't own it), but after his experience with League of Extraordinary Gentlemen
, where he ended up getting sued by some other screenwriters, he became very bitter about Hollywood.
I've heard that he liked Timm and DeMatteis adaptation of For The Man Who Has Everything
on JLU (Timm specifically approached him to ask permission to do it, something that wasn't legally necessary).