My man.. that giant ass dude can't even play with Conor properly just because of the huge size difference and he knows Conor is an athlete that relies on this to make a living, it was all publicity and trust me the Mountain can't go hard, can't grab him for real, can't legit drag him down and heck sit on him.. if Conor is let's say 30% *maybe less, maybe more* be freaking sure the Mountain is like 5-10% in that horsing around video.
Yea he probably can't fight for shit and his gas tank is empty in like 2-3 minutes and he sure as hell can't box for nothing he is just untrained and the sheer size ain't made for boxing same shit like Brock giant ass chest and feet for arms you can't expect crisp form and you are gimped by the speed and body mechanics BUT with all that said he has the strength of 5-6 Conor's and giant body mass.
There is no fight here he won't avoid him he will get entangled at some point and be dragged down where the freaking huge ass size and power will allow him to hold him down and pound him into submission he probably has like 250+ lbs on him and he has legit mass not fat mass like the dude is an athlete and is strong like an ox.
Remember that Big Nog fight vs Bob Sapp well that only had around 140 lbs difference and he was moving around like a rag in the beginning a way bigger guy then Conor for like an extra 50 lbs.. what do you think will happen if the Mountain grabs the smaller guy ? he will take him for a ride and be the end of him in 20-30 or so seconds.
Don't get it twisted here, this would be some real life shit not with rules or just "hey let's box" and I will make you miss and get you tired dead in 2 rounds then just body hit you like a punching bag before you have enough and go down.. nope just 1 single fuck up and he gets him and it's over and you damn well know deep down you wouldn't bet on this fight.