With the caveat that I am certainly no expert, my understanding is that he blew up when VIAC issued a secondary offering, which flooded the market with new shar

With the caveat that I am certainly no expert, my understanding is that he blew up when VIAC issued a secondary offering, which flooded the market with new shares at a lower price, triggering a margin call then forced liquidation. So there was an exogenous shock. Of course, the kind of mindset that would have him take profits is not the kind of mindset that got him to such leveraged paper gains to begin with.