Though a hypothesis that the collapse of the Chinese Plustoken, a classic Ponzi scheme similar to bitconnect or countless others affected the price of Bitcoin, this seem to be accceptible although it's unlikely to be the major factor but distribution of stolen funds correlate very well with market downturns.
And if we think that this is just a pyramid scheme or any scamming issue, supposedly it never takes 10 years to exist but rather to see it collapse long time ago.