You can’t call a guy stupid just because he failed at what he did and made wrong choices. He doesn’t have a crystal ball. It’s like saying that everything Blackbeard did in his entire life was useless and wrong simply because all his decisions eventually led him to being defeated by Luffy, to taking a punch to the skull and getting knocked out — and therefore he’s stupid, foolish, and an idiot.
That’s not a valid way to analyze IQ.
By those same standards, I could point out hundreds of better things Blackbeard or Oden could have done but didn’t, simply because they were “mega dumb.” Blackbeard could have killed Luffy — he had several chances to do it.