[_delirium]

Shorting a market that's recently undergone a significant price spike is actually a quite common strategy, betting that it's a temporary anomaly and will revert to the long-run trend. I have no idea whether it's a good strategy here, but it's hardly unusual. In fact, it's probably the common case: you short-sell things that you think are over-valued, and things that have undergone rapid escalations in price where your analysis doesn't conclude that the fundamentals support it are prime candidates. Lots of people made money shorting $140/barrel oil in 2008, for example; or shorting real-estate in the mid-2000s, which had been on a decade-long upward trajectory just prior to the crash.

[trotsky]

"Markets can remain irrational a lot longer than you and I can remain solvent." - John Maynard Keynes

Two things you're not taking into account: 1) There are no fundamentals in the bitcoin market and 2) Margin calls

Based on the price action of just the last few months, it's easy to imagine you might need to cover for BTC at $250 or more (log trend), yet your max upside would be $50.