A big part of it, yes, but "desire" is so broad, that it's a big motivation to do anything! That's the whole definition of motive:

1. An emotion, desire, physiological need, or similar impulse that acts as an incitement to action.

You say that violence and murder are caused for a desire for "stuff". I'm saying that violence is a means to an end. Action requires motive. Violence is one way to act on that motive. I think that violence is the primary action. We've learned to be civil over the millenia, but it's human nature to use force and violence to see to an end.