We didn’t listen to the panty bombers father either.
Or the FBI agent who thought that a group of middle eastern student pilots seemed suspicious. Especially since they weren’t interested in learning how to land a plane.
OBL is no different to any other serial killer, there was a distinct pattern to his activities. Once you know the pattern you know there is a terrorist attack coming when the pattern appears.
OBL being alive had become a liability to the terrorist, he had become predictable.