As I understand it, you are talking about trust management? In general, you are right, any trust management of your funds will lead you to losses.
Why would someone who knows how to make money on trading take other people's money for buildup? Of course, only in order to reduce his risks in case of losses, but he will not lose his money, but yours.
Relationships for one. But literally billions upon billions of dollars are given to hedge funds so that they can trade on their behalf.