One of the hardest things to do is to keep the team energy up when the other team hits lots of long jump shots. At some point, it is always necessary to let guys take long jumpers rather than press and risk layups. If they hit keep hitting their shots, the game can get ugly because the natural tendency is to try to match the long range shooting.
The other problem the Suns had was that the Kings played agressive defensive and the Suns players did not respond well. The best response to pressure defense is to pass and move without the ball. How many time did the Suns get killed in the old Frank Johnson days when teams would simply pass quicker than the Suns could scramble. It seemed like they learned their lesson and did a much better job moving the ball against the LA teams.
Was the Suns defense vastly better against the LA teams. Yes, but the LA teams missed shots the Kings were hitting. More importantly, the Suns were hitting their shots and thus not giving up a lot of long rebounds that triggered fast breaks. (Just a great defense helps the offense, great offense helps the defense.)