Paulo Costa was originally scheduled to fight Khamzat Chimaev. Despite undergoing elbow surgery and doing everything he could to stay on the card, Costa was forced to pull out of the fight. Ultimately, Costa still traveled to Abu Dhabi to watch Chimaev fight Kamaru Usman.
The fans in the UAE clearly, were not happy about Costa not fighting and decided that they wanted to still wanted to see him fight. Without an opponent, the fans decided that they would be Costa's opponent at UFC 294.
Multiple fans jumped over the security barrier to get at Costa, who threw a punch before security was able to break it off. The fans were eventually dragged away. The UFC security deserves a round of applause for amassing in great numbers and ensuring that the fight ended quickly and no one was injured.
The fans were likely upset over Costa's social media presence. Costa was able to get under the skin of the pro-Chimaev crowd to the point that they would attack him. For the fans dumb enough to pick a fight with a former UFC title challenge and security, they will likely be spending the rest of their night in jail and will likely be banned from future events.