A transfer out doesn't mean that someone bought or sold, it is just a transfer.  It could be internal to coinbase, e.g. to cold storage, or it could be someone who has purchased transferring the coins off the exchange to their own cold storage.

As far as "shake out of weak hands", for every sale there is a buyer, but I agree, everyone who has mined or bought at any point through 2020 has done wonderfully. Trading and market timing may work for a while, but people who timed and got out at $20000 in the last few months has missed a huge opportunity.