Are you looking for the real reason behind the massive declines we've seen recently?
The answer is 2 words = Interest Rate.
The US is going to keep on raising it and investors are looking for save haven that pays sure dividends ... so the US Dollar that everyone has buried in the last decade is outperforming all the Cryptos, and soon the EUR/USD will hit a parity (it's $1.25 now, it won't stay like this for a long time).
History always repeats itself, one way or another.
This is definitely a factor for the hedge funds and institutional investors. Why take risks when you can earn a risk-free return on bonds?
Also - I think people are sceptical that bitcoin can repeat it's spectacular gains. It went from $1000 to $19400 in a year. To repeat that it would need to reach $190,000, which seems improbably. As bitcoin matures the percentage gains will get smaller.