A report from last year estimates that 95% of the bitcoin trading volume is fake [1]. There's no real identity behind a wallet so bot networks can easily pump up the volume and price. Another study claims "A single actor likely drove the USD/BTC exchange rate from $150 to $1000 in 2 months." [2]

[1] https://www.forbes.com/sites/cbovaird/2019/03/22/95-of-repor...

[2] https://www.sciencedirect.com/science/article/abs/pii/S03043...