Why do cryptocurrencies have a downward trend?

In recent months, we've witnessed a notable downward trend in the prices of various cryptocurrencies. Could you elaborate on the potential reasons behind this phenomenon? Are there any specific market factors, such as increased regulation, that might be contributing to this trend? Additionally, what role do investors' sentiment and behavior play in driving these price fluctuations? Moreover, is it possible that the underlying technology of cryptocurrencies, such as blockchain, is facing challenges that are affecting the market's perception of their value? Clarifying these aspects would help us gain a deeper understanding of the current market dynamics and potential future trends in the cryptocurrency space.