Occam's razor is the idea that the simplest explanation is usually the right one. If you have an explanation that requires a sequence of random events to all occur, the probability that the sequence happened is closer to 0 the higher the number of events.
Motive is a simplifier of explanations, because now all the events in the sequence are dependent on one motive.
Now imagine that humans do some sequence of bad things, and everything in the sequence is bad. Are they just being stupid? It is unlikely, because to be stupid is to act randomly, and so the stupidity explanation would violate Occam's razor if everything they do is bad. The more likely explanation is that they are evil, because since now there is motive, this makes it the simpler explanation.
there doesn't seem to be anything here