The latest theories claim that humans gained their intelligence because they were social apes constantly trying to outwit each other in little political games in order to get the best mates and foods.

If that's true, why didn't chimps also develop an intelligence comparable to ours? Why didn't gorillas? They too are social animals, and they too engage in internal politics were they bribe/trick each other to gain advantages, but they stopped at the intelligence of a 4 year old human while our intelligence skyrocketed. Why?