By saying "one shot kills" do you mean 1 shot and the animal drops to the ground - dead, or do you mean, 1 shot and it runs a bit and drops?
I think we've all experienced both; and if you adhere to the practice of keep shooting until whatever you're shooting at is dead - you're going to see examples of, "How was he still alive?"
I hit this cape buffalo low in the right shoulder and he dropped in his tracks - blood spurting out of the entry with every heart beat. I approached from behind and he stumbled to his feet and attempted to pivot towards me. I hit him again square in the "hips" and he dropped.
Both shoulders were broken and this is what his heart looked like:
View attachment 590487View attachment 590488
View attachment 590489
Last summer in Zambia, I hit a Sable, standing looking at us, right in the chest - he reared backwards, fell - got to his feet and took off running full speed. At 40 yds he ran straight into a tree. When the skinners opened him up - his heart was mangled.
We all try to maximize our shots and minimize the risk of wounding an animal, but not all shots are perfect, nor are the opportunities. Pertaining to those videos you mentioned, was it a poor shot or was it a bad opportunity? When you've spent thousands of dollars and invested a number of days, it can be difficult to pass up a shot.
These animals are tough, living in a harsh environment - sometimes they just don't want to die.