Mir went for a take down early. I think when it failed, he started getting hit a lot--especially with body shots. That made him fearful of coming in and sealed his fate.
It's easy to say he should have charged in and taken him down, but when faced with Cigano's hands, it's a different story. He's a BJJ brown belt, but that's a brown belt under Nog--one of the all time greats of Jits.
Cigano's hands are just that deadly.