I think Occam's razor explains this: the majority of people are incompetent.

People get to positions of power through many means and very few of those are related to competence. Be it nepotism, boot licking, friendship, inheritance, people failing upwards or just plain luck, these all lead to the same result: incompetent people making decisions.

Add to that the fact that it's very easy to hide incompetency in large organizations and we have the perfect recipe for these kinds of disasters.

Even on small organizations this is common. I've seen plenty of incompetent people getting funding for startups making all the wrong decisions. They're good at selling some BS to investors and that's about it, but now they're at the helm of an organization with people under them. Another good example is people opening businesses from their successes in other areas (I made money here, now let me open a restaurant with zero experience in this industry) or even out of their parent's pockets.

Incompetence is almost always the culprit.