UFC is more than an art, it is a competition backed by an organization with opinionated rules and a huge marketing budget. It'd be like asking, "Why is Coca Cola such a big deal when we've had sweetened caffeinated drinks for centuries?"

That is such a strange question. Vale Tudo is synonymous with MMA. UFC is a brand of MMA events, products, etc. UFC is currently the most recognizable and successful MMA promotion in the world. I guess to answer your question, the UFC is a big deal because they were the first promotion to bring MMA to the global audience and have been 1000x more successful doing so than anyone else before their existence. This is little different than asking why the NBA is a big deal, why the NHL is a big deal, etc when basketball, hockey, etc existed for many years before those leagues formed.

Because marketing.. I say this jokingly but I mean it. The success of the UFC is because it was treated as a business, not as a sport.