First of all, the WaPo headline implies that those two statements are contradictory. They are not. I like a lot of people that I consider completely incompetent, because their hearts are kind.
Secondly, at the time that Trump said those things they might have been accurate, or at least debatably so. No longer. As Trump noted:
Former President Jimmy Carter is so happy that he is no longer considered the worst President in the history of the United States!
— Donald J. Trump (@realDonaldTrump) September 7, 2013
Trump really took off the pressure, so, as he noted, Carter is no longer a candidate for the bottom spot.