I have a few questions about these videos. Are the soldiers aware of the drones above them? Are these drones small and quiet enough that you wouldn't notice them unless you were actively looking for them? Why are all these soldiers lying flat? It seems like that makes them much more exposed to these drone-grenade attacks.
Sorry if these questions have obvious answers. I am very ignorant about ground combat and drone warfare, just trying to learn.
Drones are fairly loud, you can hear them unless they are a few hundred feet up if your hearing isn't damaged and there isn't a lot of ambient noise. In this case the drone is tens of feet up, so they could see and hear it.
With how poorly trained and how they are kept in a state of fatigue, the Russians have two options; wait to die and end their misery or run and die tired.
You can see the guy in the background just sitting there waiting for his turn. He isn't shooting at the drone, he is just waiting for one hell to end.
They're cleary aware there's drones above, yes. They seems exhausted, we don't know for how long they're under attack but fatigue plays it's role. They also don't have any counter-measure, and are not trained to act a certain way.
Without good fortifications hiding you from the enemy sight, there's actually not much you can do to protect yourself. At some point it's just every man for himself. You can always give away your mate position, as we can see here, it only works for a brief moment.
My guess is that he had given up on life at that moment and was probably happy that it would be a quick death as opposed to bleeding out or losing limbs.