Cathie Wood's Ark Invest bought $3.4 million of Coinbase shares on Monday through exchange-traded funds. Ark also purchased $2.6 million of Circle shares and $645,820 of Robinhood shares as all three stocks finished lower. Ark sold $2.3 million of Bullish shares. The purchases followed Coinbase's third-quarter results last week, which showed net income rising 66% year over year to $719 million.