I find it weird how many people are completely ignoring those vicious shots to the back of the head and simply saying "good stoppage."
It seems after this, every fighter out there, after they rock their opponent, should just wail away on the back of their head to end the fight. The ref isn't going to give a shit because it looks like he is protecting the fighter and the winner will be able to dismiss it as the rush of finishing the fight.
Dozens if not hundreds of fights are finishing like this. As someone mentioned it's almost like the rules are lenient when a guy is rocked. Look at Overeem vs Rogers, most hit the back of his head. If I could be bothered i'd think back and could find lots of high profile fights that are similar.