Not only did you attempt to establish revisionist history, you got it wrong. Well done.
FIrst of all, you are making a big deal out of nothing. A big man punched another big man in the face hard and he went down. What a mother fucking surprise! I mean, who could possibly have seen that coming? And this "arguably won on points"? To who? You? Ngannou lost that fight, and if you knew anything about boxing you wouldn't even have tried claiming that. He put up a valiant effort, especially from a boxing novice and performed way better than most expected of him. That may have endeared him to the fans, but that is certainly not a boxing win.
Secondly, even if he does beat Joshua, so what? That won't ruin boxing or even take away from it and it won't make MMA better than boxing. Fans love the heavyweights, regardless of whether it's boxing or MMA, because they are big men who hit hard and quite often their fights end in spectacular KO"s. Sure, most of the times they are sloppier, have poorer cardio, and rely more on power than technique, but fans don't give a shit. They want highlight reel finishes. Joshua can be chinny and Big Frank hits hard, and he can take a punch. If Ngannou beat Joshua, I really wouldn't be all that surprised personally. Like in the Fury fight, I don't expect Francis to win, but it would be cool if he did. It won't disillusion the boxing world, but my fuck it will be funny to watch Dana squirm in the pressers after that.
Put most of the UFC lighter weight fighters in boxing matches against their peers of the same weights... what do you think happens? I would suggest the heavier the MMA fighter is, the better his chances are at pulling off the win, simply by virtue of being a little more durable and a harder hitter.
Put Henry Cejudo in a match against a top-10 boxer or champion of the same weight class, and he'd get annihilated. The smaller guys are much faster and far, far more technical. Their success comes via output and usually on points as they have less KO power than the heavier boxers.
If anything, Ngannou's winning will not diminish boxing, but it will make all the other MMA fighters have second thoughts about locking themselves into restrictive contracts and consider exploring other options to earn.
I am actually more excited for the Joshua fight than I was for the Fury fight.