It was partially Alexander's fault.
In the original timeline, Alexander didn't exist at all. In this labyrinth, those two unnamed men were meant to die, and while Luciel and Lucifer would experience loss and injury, they weren't supposed to get anywhere near a fatal wound.
This was because Alucard and Commander Huo had more than enough time to save the two of them after killing the clones that attacked them.
The two who died would have died regardless. They couldn't hold out for more than a minute against their opponent, so no matter who tried to save them, their fate was set in stone.
Even in a situation where Alexander stepped in and killed the enemy, they would have died in the near future due to some unavoidable circumstance or another.
Some people's fates were set in stone like that. Those kinds of fates were precisely what the Saint Emperor fought to change, but not even Damien's main body had the power to do so yet.