They trying to rip his balls off thats why he keeps sitting down, hyenas are cowards.
Lions will do the same to Cape Buffalo when they're hunting. It's a glaring weak point on male mammals. But yes, they were all going straight for his nuts every time he moved. If they would have gotten them, he probably would have gotten killed. Hyena have ridiculous bite force and that lion would have been fucked. Even if he managed to survive once his brother joined in, his nuts would never function again.
Why are male lions or whatever the strong ones then? Females dont have this nut problem