It was never anything but a line of bull, and it was never a reasonable conclusion to hold. Had it been, none of the professionals would have continued to look for him.
Professionals? If you mean black ops, then they would have been operating in something called “secrecy”. Which means that whether Obama was alive or not, or where he was, would have been something kept obscure.
Besides, I doubt that until a real DNA match was done, nobody was really 100% certain, eh?