Give me your best conspiracy theories!

There are so many easily disproven, low-IQ conspiracy theories floating around on the internet.

Examples: - flat earth theory - chemtrails - faked moon landing - Finland doesn’t exist

Just to name a few. These can be funny and I do enjoy reading about them, but I want to hear what theories people have that are high-IQ, well-thought out, and will give me pause. Let’s hear it!