Imagine there are only two shares GME.
You buy two GME for $1ea. Two short sellers needs 1 GME each lest they hemorrhage money on fees. You loudly announce your plan to hold half your GME forever. The short sellers trip over each other to pay you stupid money for the one GME you are selling. You then sit on the other GME for awhile, maybe sell it in a year or two for a buck. In any case despite buying two and selling one you've made a ton of profit.
Now scale this up to several million people.
