It's not that they don't believe in Bitcoin, the reason they sell Bitcoin is because they want to make a profit from the transactions they make, so in this case they use the law of "buy at a low price and sell at a high price". People who sell Bitcoin cannot be judged as having no confidence in the asset, they are simply taking advantage of price fluctuations to make a profit.
Investment strategies are not only long-term, when they have reached the specified time limit and obtained the desired profit, they will immediately sell it and then re-enter when the price is low.
I didn't those people who were doing short-term trading professionally as because bitcoin has the volatile market, so there is nothing wrong with that doing short-term trading or booking profit by selling bitcoin.
What I mean there is meaning those peoples who don't have knowledge about bitcoin as well the analysis skill but they intend to invest in bitcoin only following the trend as well those people and also those who don't have knowledge about the bitcoin easily distrust bitcoin if it's price drops.