Imagine that there is a race of spacefaring aliens dedicated to keeping peace in the Galaxy. They recognize that the people of earth are a violent, dangerous threat and should be prevented from making it to the stars.
They don’t need to wipe us out. They’ve recognized for thousands of years that we were dangerous. So they infected us with superstitions & paranoia while at the same time increasing our abilities to make advanced weapons of war.
They suppress our abilities for critical thinking and empathy. Then, they gradually increase our dose of conspiracy theories and cult behavior.
The problem takes care of itself. If we don’t tear each other to shreds, we make our planet uninhabitable. Ideally, both, because what’s left behind is a monument as a lesson to others.
It’s the most believable theory yet!