The thing is, people are not fully in control in a striking exchange, because the movement partly so fast that it is beyond the reaction time of their nervous system.
That's why you occasionally see great strikers getting KOed by mediocre strikers, but you will almost never see a great grappler getting submitted by a mediocre grappler (gotten beat up before aside).
Of course, it's not pure luck if a mediocre striker KOes a great striker, because he has trained to strike, but there certainly is a luck factor in it.
Striking is maybe comparable to poker, where you can train your calculating abilities, psychology etc., but still there is a luck factor. A good poker player would win most of the times, but even a complete beginner could win if he gets good cards. Grappling is more like chess where the better player would basically always win against a weaker opponent. That's because your brain can react much faster on tactile information than on visual information.
I don't agree with this fully. I get what you are saying by how for split seconds no fighter can react in such manner to fully use his skill and technique. But Anderson pretty much never lets anyone get lucky...and he strikes all the time...and he lets people hit him.
And you are not factoring in gameplan or predictability in fighting. Sure some elite strikers get beat by average strikers. You may say a perfect example is Gonzo/Cro Cop? Seems like a nice example right? But CC didn't expect a high kick from him. He expected him to try and work his Jitz. That is a larger reason why the better striker got caught than any luck. Gonzo most likely practiced that. He had the balls to try and throw it vs. CC and timed it perfectly. You know how hard it is and how good you have to be to time and reach a high kick? Gonzo was smart enough to do the unthinkable. He threw the kick, so he intended on landing it. It did. The better striker in not going to always win...they aren't machines. But luck really isn't the word when Gonzo out smarted CC and landed a high kick. It isn't like CC has never been caught by lesser striker in practice. Every exchange in a fight is different.