Basically the ELI5 situation is this:

There was a company about to go bankrupt.

Many big firms started short selling way beyond normal levels.

Some redditors noticed this and started buying up remaining inventory and refused to sell until it hits an outrageous price.

Because there are billions of $ short, these people need to pay up, but there's not the inventory, which drives the price higher....

But not enough people are selling.

This creates a loop where the price continues to just rise and rise.

The Hill