He got the snot knocked out of him with the nerf bat, that is what. Malphite is stronger right now (I play both frequently, my two favorite champions) because his damage is better and his initiation is SOO GOOOOD. Maokai doesn't deal any real damage anymore, and that is problematic for him. Sure he is a tank with a ton of utility, but when another tank (Who actually hard counters most ADCs) does his job, just better, then yes he will fall off. This isn't to say Maokai is bad (He's not, I still enjoy playing him, just like before the buffs) it is just to say that he isn't number one at his job right now. Malphite and Maokai also serve veeery different roles throughout the game, Maokai is all about team fight utility and CC, while Malphite is better at Hard engage and burst damage output.