I think it has to do with the way the human visual system effectively does edge detection and then groups those into objects and attaches meaning. When you are extremely sleep deprived, the edges gets grouped differently and you start seeing things that aren't there.
I could judge what was real or not based on likelihood of me seeing said things in the wilderness, or if I got close enough I would be able to tell what I was really looking at. Another runner later informed me that I had told him he wasn't real when he passed me.
I once saw death (exactly as most of us imagine it, dark robes and a scythe) while driving on a highway late at night, I understood the message my brain was sending me: I just took the next exit and slept for an hour (it was too cold to sleep longer, but it made a big difference on my concentration anyway).
It doesn't even feel that bad once you get past the slump in the 20-24 h region.
Later Hominids are meant for this. Without being able to pass long time chasing our prey to the moment of its exhaustion, we'd not have been able to secure the cholesterol needed to further evolve our brains.
Small fish/shrimp can appear to "teleport" since they dart away so quickly, but if you harass them enough, you exhaust them into a state of shock. It's no longer a chase, it's a harvest.
Even in manhunting, you get nowhere chasing the subject since you move at the same speed and the element of uncertainty tilts in their favor. So you try to anticipate where they're going and ambush them there. You turn the chase into a trap.
We're apex predators for a reason. Exhaustion chases don't make sense.
The hotter the weather, the easier this gets.