Reddit wanted to break the boomers money by presumably increasing the value of a company that hedge funds tend to short. This caused fund managers who have less fortitude to also start buying the shorter stocks in order to cut their losses, further increasing the value and causing a spiral of increasing value and short sellers cutting their losses by buying the stock.
Apparently the price of GameStop shares have increase 300% per the last few days.
Edit: even more than that apparently.
Anyway,
the term for it is short squeeze.