Best president under what constraints? Were they rating presidents on their compliance with the constitution or their popularity?
Given that those in Academia, most especially those who would be assessing the historical rankings of Presidents, are known to be near universally far left in ideology, you would expect those academics to favor those Presidents they judged to share their own values and what would be judged to be great accomplishments.
Those same academics who voted most likely believed the long accepted hype that FDR got us out of the depression. Had they been taught or been exposed to the UCLA studies showing that this was indeed all hype with little basis in reality, the vote might have gone very differently.
To evaluate it with any accuracy, one would have to know what criteria was used to rank the Presidents. Certainly leftist historians or political scientists will score each man much differently than would conservatives in virtually any discipline.