As far as I know that is how trading works, that's why people need to be very careful on a trade that they're going to make because any amount that they'll buy will be a profit for someone else. For example, certain coin gains over 30% to its price and some people gets FOMO and bought at higher price that could be a profit for those who placed a sell order at that price and those who got FOMO loss because the price didn't go higher anymore. It's just like, in order for you to gain profit there should be someone else to lose.