A significant portion is sold into stablecoins which are other cryptos. If the stablecoins go above their peg, then it is more profitable to mint the stablecoin

A significant portion is sold into stablecoins which are other cryptos. If the stablecoins go above their peg, then it is more profitable to mint the stablecoin at the issuer with dollars you own on the exchange, and sell the stablecoin immediately to the panic sellers clamoring for stable value. Many other assets are merely priced in bitcoin and their dollar value can fall without a single trade occurring. This needs to be fixed sector wide. And finally, people have unlimited withdrawal limits to fiat or crypto from exchanges. You need to convince your exchange to raise yours or get another exchange. OTC desks have no limit which is what institutional traders use.