The explanation for this (according to Jonathan Haidt) is that early humans developed weapons like spears and axes, which made it easier to kill other humans. So it is relatively easy for a larger, stronger alpha male chimp or ape to dominate weaker males, but a human alpha male bully would often end up getting speared by a lower status rival.

That sounds pretty similar to the argument that high gun ownership makes makes it more difficult for the government to become tyrannical.