Actually bitcoin is like others coin so its price can be high and low. So if people see that the price of bitcoin is high so they can sell. They can save something for the future also. There is nothing as stupid decision.
in the trade there are two things we must remember between selling and buying there is a risk there is also a profit and there is a loss, all oang would dare to buy a lot when the price is cheap and when expensive people are ready to sell, because the goal wants to earn profits.