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.