BJJ isn't magic, i am a purple belt and it's not easy to sub someone from the guard, no gi even harder, at heavyweight and at the highest level in mma where you could stall all day if you are on top it's almost impossible.
There is a reason you barely see submission anymore in mma and even less at heavyweight, it's not because the level went down, it's the opposite, the level got up and nobody is willing to play on the ground anymore because if you are on bottom you are losing.
I haven't seen Kharitonov against Werdum in ages, but it's easy to shut down someone from the guard if you are on top, just put your hands on their biceps and stall, you could do that even if you are clueless.
This is a great seminar Cormier and Velasquez did in Russia (and it's free, god bless the internet).
At 34 minutes Cormier says that at the highest level in mma nobody want to play guard anymore, they want to stand up, and Crazy Bob Cook on the bottom says" we want them to play guard".
You play guard in 2017 and you lose the fight, unless you are a freak with no articulations like Brian Ortega that can catch submissions from anywhere.
This is a folkstyle drill at AKA, the guy on bottom wants to stand up, you see Cain wrestling with Todd Duffee meanwhile Cormier says to someone "get up, forget that jiu jitsu shit".
Nogueira had poor wrestling, there is not way around it.
That takedown against Kharitonov was bad, you don't go to your knees in mma, and at heavyweight you are asking to get sprawled and carry a big ass man on top of you, if the guy know how to wrestle, unlike Kharitonov.
Cormier says the same thing in that video i linked above, if you are interested.