@ysmina-- I'm no an expert on economics. But I don't think it's a problem for there to be a brand leader or market leader in a free market.
You are right that in a free market, no single player should dominate the market as a whole. But that actually means that all players should have equal opportunity to participate in the market. But it's natural that in a market, some manufacturers will do better than others. If a brand or company continues to have the highest sales and the most customer, we can't really say that it's a monopoly. It would be a monopoly if the rules were unfair and if the other companies were not allowed to sell more or make more money. At least, this is how I understand this issue.