Warren's just following his old philosophy when many are still euphoric after Trump's winner in US election, then he took advantage to sell his asset at peak.
Honestly, now is the wrong time to buy Bitcoin. Anyone who is buying now should've bought a month ago.
Although, if you are looking to sell off some of your holdings to get some cash, now is a good time. I just sold about $500 worth of BTC. Zero regrets whatsoever. (And I still have a huge stash.)