Going into the Silva fight, roided to the gills, not even trying to cycle, when cycling was easy, no random testing, usada was nowhere to be found (the good ol times). He purposely went into the fight knowing he would get caught. So even if he had won, that belt would have been taken away from him the very next day. Sonnen just wanted to hold that belt so bad, even if it is for a day. For one day in his life, he wanted to shine. Its all that mattered to him. So what if he gets busted and has his belt taken away immediately. He will have a story, he is the guy who beat the invincible Anderson Silva, but some silly commission took his belt away. He was coming with a vengeance, to get what was righteously his and the rematch would earn him millions. From business stand point, it was excellent decision.