In fact, I think such a thing should be considered normal, and there is nothing to be curious about and incomprehensible. Everyone's cognition and understanding of everything is different. Maybe your friend knows more about the fund, so he made great efforts to buy it. Maybe your understanding is not so profound, so they often fall down. Moreover, the problem of luck I just mentioned really accounts for a large part. Don't think that luck is a trivial matter, it really isn't. In fact, it is very real and important at some time.
If you don't think luck is important, then why do some people win 5 million in the lottery and you can't even win two dollars? This is actually a big question of luck and probability. If you think your friend is more experienced than you, or more capable than you, then you can learn from him. Anyway, we are all friends, and I believe he should be happy to tell you. What's wrong with making money together?
If you don't want to ask him, then you can observe the characteristics of the fund he bought and learn more. Don't buy blindly. You must know clearly before you can make a decision. Don't watch others buy this, you buy this and others buy that. And to be honest, there is not much difference between funds and stocks, and there is not much difference between funds and gambling. It is impossible for everyone to win.