I will not give you obvious reasons. But I can say with confidence that the cryptocurrency market is cyclical. And he's an unstable person. We see prices rise and fall again and again, and that's normal. But from year to year the price increases.
In my opinion the main reason is this that the price of bitcoin is down and as we know that bitcoin is the leading crypto in the market and also pioneer crypto, most of the people like and trust bitcoin the most and put their money in it. When they sat aside it means that crypto market is going down. For investors first option is bitcoin and then other coins.