Thought experiment: Guaranteed riches with BTC ????????????

Say you have two friends, lifelong buddies, would do anything for each other, trust each other more than they trust themselves, etc. Both have decent life savings, but nothing to write home about.

The thought experiment: What if both agree to dump all their life savings into BTC with infinite leverage, one goes short, the other long. Literally every penny they have. What will happen with certainty: One will get liquidated, go to zero and lose everything. The other? He will make MILLIONS. He takes the winnings, and splits them with his friend. They are guaranteed to have more money combined than when they started, probably face melting gains. The downside is zero, the upside is limitless.

What is wrong with this scenario and why hasn't it happened before (or has it)? Seems simple enough, a can't-go-wrong get rich hack. Unless I am missing something, enlighten me if so.