While I see their hypothesis that the decline in bitcoin from 20k to 6k was related to the introduction of the futures market there are lots of details that seem iffy. For example:
Bitcoin had many crashes in previous years
The dotcom boom had a fine boom and bust in spite of there being a futures market
The US housing bubble also did a big boom and bust without a good futures market or way to short houses (yeah I know some people kind of did by proxy in The Big Short but it was hard)
"price will be set by the most upbeat buyer" is kind of wrong. The price will be set by dealing between the largest buyers and sellers. If people are selling millions worth at $6k some guy who thinks its worth $100k but who only has $1000 to invest isn't going to move the market
You've been able to short bitcoin on BitMex since 2015, though using crypto rather than fiat
Bitcoin had many crashes in previous years
The dotcom boom had a fine boom and bust in spite of there being a futures market
The US housing bubble also did a big boom and bust without a good futures market or way to short houses (yeah I know some people kind of did by proxy in The Big Short but it was hard)
"price will be set by the most upbeat buyer" is kind of wrong. The price will be set by dealing between the largest buyers and sellers. If people are selling millions worth at $6k some guy who thinks its worth $100k but who only has $1000 to invest isn't going to move the market
You've been able to short bitcoin on BitMex since 2015, though using crypto rather than fiat