Well, it's natural to be mad if such thing happened but just think the other way around. What if you lose if you insist your choice and your friend just avoided the worst and you ended up being grateful to him.
Basically we never know how lucky he is if he bets and doesn't avoid it. Maybe he could win it, and maybe he would lose because winning and losing are just possibilities. I have heard the same thing from several gamblers, for example if I bet $5K on Saudi Arabia's win over Argentina then maybe I will win $500K at the end of the match.
In fact, I often try friends' suggestions in betting that there is a loss in the end, there is also a win and I thank him, this is indeed winning and losing is just a possibility or it's called luck if a friend guesses and we follow it but we have to be careful that it's luck the rest can be valued which one is better for your own bet.
I thought that what if someone bets on Saudi Arabia maybe he has won 100x from the bet placed, but I'm sure a lot of people will choose Argentina in that match.
