PixPix, it may not have even been for something that you did. This game isn't just about what you're doing but also what people perceive you're doing, so the Mafia may have thought something of you that wasn't even true because of something you did. So in addition to considering your actions, you also have to consider the possible ways they'll be interpreted. It's tricky!
But hey, as I always say, the best players tend to get killed early. Maybe you should take it as a compliment!