I think it's more comforting for people to believe that there are a handful of evil, mustache-twirling villains, sitting in a smokey room, plotting and directing their henchmen to carry out a conspiracy. "There are only a few bad guys, and the rest of us are just doing what we can," they can say to feel good about the world.
It's a lot more scary to admit that there is no evil puppet master running things, and it's simply that the vast majority of people in leadership positions are just awful people, acting independently, but aligned with the rest of the awful people, intent on doing whatever it takes to make line go up and to the right.
Honestly, I wouldn't even couch it as the majority of leaders being evil: it's that the systems they lead, and that we all operate within, are poorly constructed, broken, or outright corrupt, and need a concerted effort on all our parts to fix them so that they actually work for everyone, rather than funneling wealth and power to the already-wealthy and already-powerful by default.
And that's genuinely hard! Just by the nature of things, it is much, much easier to create a system that reinforces existing power structures than a system that works to subvert them and give more power to those who have little.
The mature perspective is that there isn't one big conspiracy. There are many small conspiracies.