The French thinker Rene Girard had a seminal insight which has shed light on just about every aspect of human endeavor from theology and anthropology to economics, politics, psychology and business development. It’s called mimetic desire which being translated is “imitation envy”
Basically it is the observation that we learn by watching and imitating others, we desire to be like the other and before long this leads to rivalry and competition. Johnny watches Jimmy playing with his toy trucks and Johnny is soon pretending to play with toy trucks too, but the problem is he doesn’t have any toy trucks, or he doesn’t have nice shiny new ones like Jimmy so he not only imitates Jimmy he covets Jimmy’s toy trucks and this, of course, may lead him to steal Jimmy’s toy trucks when Jimmy’s out of the room or if he can’t wait and is not sly and is actually bigger than Jimmy he goes over, knocks Jimmy on the head and takes his trucks.
This scenario is perfectly portrayed in the prologue of the third Lord of the Rings film where we see Smeagol steal the ring from his cousin Deagol–after he murders him.