In sports-betting martingale strategy won't decide if you will win the game but the team or player you put your bet on. Maybe it is just a coincedence that you used martingale strategy that time and luckily you won. The one that will decide if you win in a game is your analyzation of opposing teams. I think martingale strategy only works on dice games but only once because if the house notice that strategy you used then it won't work again next time.
I don't see a problem here. I think you are confusing the terms. Martingale will just be a betting strategy and it has nothing to do with analysis of the game. He will do that as well, or at least I hope he will, because that is crucial in sports betting. Of course that he can't guarantee a win, but if he uses martingale, and since he will get in profit every time he gets a bet right, that means that if he chooses the games right, he will reduce the effect of bad luck in a game or two. So I really think that the only good option to use martingale is in sports betting, and not in dice. In dice sites, it does not matter what you do. The house has the edge, and in the long term, you will lose, but in sports betting, it makes perfect sense.