If you won $100 on the financial markets, know that someone else lost $100.
If you lose $100, know that someone else won $100.
Because trading is a zero-sum game. The money you keep or lose does not come from central banks, but rather from us individuals. We are the liquidity. And the big players in the market manipulate us as they wish.
This explanation is not entirely true because it is not every money that is won or lost that is going or coming from another trader. When we decide to buy or sell a coin, we are also interacting with investors and not just traders. You might decide to sell Bitcoin at $100,000 and someone else who has a longer term investment plans could be buying at that same price and in this situation, neither of you are at lose because while you think it is another trader that is buying your coin, it is an investor that is willing to hodl for some months or years and both of you are going to be making a profit from that transaction. In most cases it is what you explain that usually happens but still the seller can decide to hodl the coin instead of selling it and turn himself into an investors to make profits.