Where does the money for shorts come from?

With normal “longs” it's easy, money is pretty much only exchanged between buyers and sellers with banks as middle men.

Going from the colors in Tradingview, with “shorts” you set up a “sell”. The price goes down and you get money when you “buy”. How does it make any sense for a bank to give you money for decreasing funds? What do they get out of this arrangement?

I feel like I could accurately predict a ton of different stocks moving downward and am using paper money to validate that. I am just curious why/how we get money from banks in short sales.