Buying or selling Bitcoins (BTC) or other popular cryptocurrencies does not take place only through publicized exchange platforms like Coinbase or Binance.
Large amounts of BTC transactions are executed in more discreet environments, the so-called “over the counter” (OTC) transactions, where the parties don’t want to disclose their identities or influence the market value, or simply believe they will benefit from better conditions...
https://en.decentral.news/bitcoin-otc-overview-of-a-nascent-and-sometimes-scary-market/
