The crypto currency market is highly volatile and can fluctuate greatly in a short period of time. There are many factors that can contribute to a crash in the value of cryptocurrencies, including:

1. Regulatory changes: Governments and financial institutions may introduce regulations or restrictions on the use of cryptocurrencies, which can cause the value to drop.
2. Market sentiment: Negative news or sentiment in the media can influence the perception of cryptocurrencies and cause the value to drop.
3. Hack attacks: Cryptocurrency exchanges and wallets are vulnerable to hacking, which can result in the loss of large amounts of cryptocurrency and cause the value to drop.
4. Profit taking: Some investors may decide to sell their cryptocurrency holdings to take profits, which can cause the value to drop.

It’s important to note that the crypto market is highly speculative and the value of cryptocurrencies can be affected by many factors, both positive and negative, so it’s hard to predict the exact reason for a crash.