For me it could also have been a coordinated attack. I would like to know whether right before his tweet there were some suspicious shorts on Bitcoin in the market or whether he really posted that message against Bitcoin without letting anyone know in advance.
These things were planned well in advance and Elon is not some innocent little kid like many would like to believe. There is no point in looking at the orderbooks for Bitcoin, as BTC is very difficult to manipulate. If you really want to find out who benefitted from this, then I would advice you to check the exchanges where Dogecoin is being traded. For the past several months, whales have been accumulating DOGE. And the price was being kept artificially at a high level, even before this tweet. It is possible to manipulate a coin such as DOGE, which has very low liquidity. But the same is not possible with a cryptocurrency such as Bitcoin.