Most of the time it is quite hard to predict the market changes of cryptocurrency. This means we don't know what's gonna happen the next minute. It can go high, else it can drop low. So people look for an opportunity to make an investment or buy it rather than predicting. In such a way now the price is moving gradually in the upward direction which assure profit. This is the reason for people to invest when the price is going up.
When the market rises, investors sentiment will become optimistic, and it is a good time for them to decide to buy. I always prefer trading when the market enters uptrend because if there is a good strategy, it will still make a small profit during that time. Of course, do not be too greedy when investing because any of your mistakes will affect your assets.