Maybe because they weren't total a**hats and behaved in a professional and dignified manner as a president SHOULD. I mean, Bush may have been a complete dope, but at least he didn't act utterly undignified, disrespectful to allies, other world leaders, or put shame on the seat of the president.
I didn't care for Bush, but at least he wasn't a manchild shoving other leaders aside and b*tching about the news not coddling him enough. He still cared more about trying to get work done rather than obsess about ratings. It's a shame that he looks pretty good now in comparison to Trump.