On the former point, Coinbase is not the largest spot bitcoin exchange. It currently sees somewhere around 2.5% of global daily trading volume, according to BTC/USD trading pair data from CoinGecko and CoinMarketCap. You can quibble about the details, bitcoin trading exchange volumes could also include trading pairs between many currencies, crypto or otherwise.
Source: https://www.coindesk.com/consensus-magazine/2023/07/13/the-unfortunate-conclusion-of-picking-coinbase-for-the-spot-bitcoin-etf/?utm_medium=referral&utm_source=rss&utm_campaign=headlines