I know it's been done to death, but I haven't seen this done yet, so I figured it might add something. I broke the gif that we've all been looking at into frames. It has 216 images total. I've just pulled out some key images. We can always look at more, if people feel like it.
Anyway, here's what I'm seeing:
This is before the punch lands, just to get a frame of reference on Cain's posture, etc:
This is, as far as I can tell, the punch landing (I don't see Cain going limp):
This is Cain reacting to the punch (to me it looks like his head has snapped up, but he still looks alert and like he's still in control of his body, which has still not gone limp):
This is Cain stepping with his left foot, just before the left foot makes contact (to me, it doesn't look like he's out, or like his body is limp):
This is Ngannou coming across Cain's face with the forearm and pushing toward Cain's left foot which is just touching down (to me, that right knee looks to be driving, not collapsing, as some have suggested, but Cain does seem to be landing that left leg rather gingerly even as it just touches down):
This is the moment Cain's left knee buckles (to me he still looks alert, but his body is definitely going loose here, to my eyes as a result of the knee collapsing and Cain reacting by trying to release tension):
This is Cain falling back (to me it looks like his body is just collapsing away from the buckled knee, and he still looks alert to me, with no sign of a KO that I can see, flash or otherwise):
This is Cain's body really beginning to crumble over his knee (again, he looks alert and, to me, looks to be starting to cry out in pain at this moment, and not when he wakes up with his knee twisted under him as some people are suggesting):
Cain either collapsing over the knee or going limp even further, depending on your perspective (to me it still looks like he's alert and his knee is just buckling under him):
And this is the last frame of the gif (unfortunately, because I think there's more to gather from how Cain actually lands and reacts):
Anyway, I know that different people will look at these images and see different things. That's just what I happen to see happening. I figured either way, since it's such a contentious issue, we might as well try to take the closest look possible.
Honestly not looking for a fight. Just open to discuss further and more precisely.
Discuss away.