They didn’t have an exhaust fan hooked into a nearby vent hole, because they didn’t have exhaust fans. The rest of your post is similarly speculative opinion.
Perhaps but help me out, where did he address ventilation anywhere? If he did, I missed it in the description.
The rest of your post is similarly speculative opinion.
Where was there any speculative opinion? The presenter is the one who said the fissure opening was up nearly four stories on the side of a cliff.
So, as part of these creatures funeral transport, the body would first have needed to be somehow carried to the opening nearly four stories up a cliff face. Perhaps a body could have been carried down the cliff face to the opening but we are not told how much farther up from the opening the cliff went.
Whether by climbing the cliff face or descending, once at the opening, there was no possibility of reverent carry. The body had to be pushed-pulled-dragged in inky darkness through "a chute" averaging less than 8 inches but at times as little as 6-7 inches for 250 meters.
That's his explanation not mine.
That was a lot of energy expenditure.