When asked via Twitter why he released Okami, UFC President Dana White remarked "Our roster is packed." When asked by Yahoo Sports why he was releasing a highly ranked fighter who had won three of his last four bouts, White responded: "He was always a tough guy and was right up there, but it's almost like he'd become a gatekeeper. I like Okami, and you've heard me say this many times, that a win over Yushin Okami meant something ... But he was never able to get over the hump and win one of those [significant] fights. We have a lot of guys coming in and I've been saying this all year: We have a full roster and there are guys who deserve opportunities. When you bring guys in, someone has to go. That's why these fights are so meaningful."
So, that's why according to wiki. And they only brought him back for this card because he didn't need to get a Japanese visa on a week's notice to save the card.