The share the short sellers are selling are borrowed from the available share. That is, if I want to short GME, I am borrowing someone else's GME shares to do it (and will repay them in GME shares). So the total demand should also be going up.
Imagine this situation. You are super bullish. I am super bearish. So I short 50% of the company directly to you. Okay, $$$ has changed hands, but you have the same number of shares and I have the same number of shares. You just also have a promise that I will deliver more shares to you in the future. I might make or lose a fortune delivering them, but I haven't altered the total amount of shares in the world.
Imagine this situation. You are super bullish. I am super bearish. So I short 50% of the company directly to you. Okay, $$$ has changed hands, but you have the same number of shares and I have the same number of shares. You just also have a promise that I will deliver more shares to you in the future. I might make or lose a fortune delivering them, but I haven't altered the total amount of shares in the world.