The video is a bit frustrating, he's rewording the exact same few points endlessly, and only shows the actual clip once (admittedly, I didn't make it to the very end), where you kinda don't see shit.
But unintentional clash of heads happen, and you can't just substract the sequences that follow and do a re-judging weeks after. If we did that with every controversial fight (about every other fight, it seems), MMA would become a shitshow (well even more).
I guess the ref could've stopped the fight, leading to a NC, like it happens sometimes, etc etc. But the fact that the fight went the distance shows that both fighters were still able to fight, and people, and the UFC, don't want to see fights stopped at the first opportunity, it benefits no-one.
It does sucks for Curtis if, in an imaginary world, he would have won had the clash of head not happened (which we don't know for sure), but that's how it is.