I have flown the DCA visual many times, and the White House is not visible at all from that direction - not compared to the mall, the Capitol, Wash. Monument, etc.
He probably was too high on the first pass, was right over the target before he saw it, made a "fighter type" turn to come around for another try, exceeded 45 deg or so of bank and stalled it. Anyone who has done steep turns in a heavy sim can confirm that you get the shaker a whole lot quicker than you might think. The impact on the Pentagon was just dumb luck.
On another note - religion has at times gone perverted and killed people, but secular humanism has a much higher body count, from the Third Riech to the killing fields....