Of course none of can say one way or another that MK is the that killed Lizzie and Lyric but seeing his history kind of helps make the random abduction/crime of opportunity scenario in the L&L case look more plausible to me.
MK seems to be the type that plans a little bit but does not care who is victims are. Random girl outside the bathroom, random woman driving her car, random girls outside his apartment...
I can see him sitting at Meyer's Lake just waiting to see who showed up, all the while knowing that whoever got into his vehicle was going to end up hurt or dead at 7 Bridges. As he sat, 2 girls came by on bicycle and he was able to convince them that they should allow him to drive them home or whatever story might have worked. From there, with victims in tow, he headed straight to 7 Bridges as planned.
I had trouble visualizing a scenario like that before I read about MK because I assumed that the perp would have planned more. But maybe not... maybe the perp really was just waiting and L&L were in the wrong place at the wrong time