William Lear, just by himself, ain't credible. William Lear, with his associate who helped create the bogus document, with a signed and notarized document from his lawyer attesting to the origin of the "O.H. Krill" document (they made it up in the lawyer's office), AND taking some serious steps during the videotaping of a TV show to save Bill Cooper from major embarrassment...yeah, that's a wee bit more credible than Bill Cooper's sudden about-face for no readily discernable reason.
Bill Cooper had a habit of simply repeating what known UFO charlatans were saying as Gospel Truth, based on his alleged knowledge of "classified intelligence documents." He got caught in a major blooper as a result. End of story.