I think that the trouble is that high school teaches people how to follow, so they are conditioned for that. When people get to university-level education and, even more so, complete a masters degree, they have access to all sorts of information which the average person will find very difficult to obtain. The other aspect of this, which I would argue is far more important, is the social connections which are available at the "upper" end of society. It's all an old boy's club and semi-closed culture which most people simply don't have access to.
Leading is a skill just like mining or programming are skills - they can all be learned. Given the recent evidence of life-long brain plasticity, it's reasonable to assert that this is more a problem of nurture than nature.
In short, we train relatively few people to lead, hence the low supply.
Not to mention SCALE. While it's hard to be sure about cause and effect, a CEO who is 10% more effective than their peers can generate more shareholder value than a developer who is 10% more effective than their peers. A CEO who is 5X better is pretty much priceless.
Anyone can hit rocks in a mine. It might be hard and stressful work, but anyone can do it.
Not anyone can make decisions and lead an entire group of people.