Bitcoin falls due to the fact that the following scheme occurs on the exchange, the number of those who want to sell crypto currency exceeds the number of those who want to buy it, that is, the demand exceeds the offer, as a result, there is a situation with rates and futures orders (so-called orders) for which the number of people wants to buy or To sell in the future the number of crypto-currencies for a lower price increases.
It is technically possible that some crypto currency will be replaced by bitcoin, but so far there are no such candidates