There in lies the difference, these are all pros that get paid to fight MMA. Matt Serra was a capable fighter. A vet. GSP was still fairly young, had all the confidence at the time...
And these were precisely things outside of Serra's control and arguably worked in his favour. This isn't about how lucky if at all, Serra was, but determining that dumb, at the moment intention, somehow nullifies the luck factor.
It also would matter exactly how effective or or good your kick was. Is it world class?
It's pretty shit, but it doesn't matter. Most people's striking is shit compared to Silva's. Hence, if I hit Silva, even though I trained the kicked and intended to hit Silva, really, its because Silva or the circumstances of the fight somehow favoured me (luck) that would have been the reason I connected.
Similarly, Maia's striking is relatively shit compared to Silva's. If he knocked Silva out I wouldn't say he could replicate that performance again if they fought 10 times.
If Damien Maia intended on subbing Anderson (which he was) in an MMA fight...and pulled it off...I wouldn't call that luck. He is a BJJ Ace and trained to do that. As much of an MMA upset it would of been...it wouldn't of been luck.
Sure, because Maia's BJJ game is much better than Silva's. But it would depend on the circumstances of the victory. Like if Maia had perfected his takedown game and was able to gain dominant positions. No one would call a sub from those positions lucky. He's Maia, thats what he does. But you can't tell me that the Ryo Chonan sub of Silva would be equally 'non-lucky' as the described Maia one. One was likely a desperate attempt (though intended), one was part of a dominant strategy (also intended). What is important here? not the immediate intention of the act, but the forces gathered before the fight.
Serra didn't have world class striking. But he was more experienced. He wasn't as young and naive. He had nothing to lose. It isn't out of the question that he was simply better that night and was more game for the fight.
Again, no one's denying that being in the UFC doesnt take skill, as I said before, your luck depends on the relative
skill to your opponent. Arguably, Serra even came into the fight with a superior strategy to beat GSP, again we're using the fight as an example, but again, play that fight 10 times and ask yourself what happens.