The poll is asking who the best president was, not your personal favorite. By all calculations, Carter was a massive failure.
So was Ford before him, and Nixon/Reagan/Bush Jr ran unprecedentedly corrupt administrations- took a New Yorker Businessman to top them.
This leaves the possibility of Clinton or Bush Sr being better presidents, but given how much damage they did with all those foreign wars, and given how the former squandered himself with a b*()j*% and the latter sat on his hands during a much more manageable recession....Carter still wins by any objective measure.