How is it ironic the way Remarque kills off the characters of Paul and Kat?

Towards the end of the novel one thinks these guys might actually have a chance. Kat and Paul, whom we have gotten to know so well, are nearing the end of the war. All their comrades are dead. They have been through multiple hells and multiple baptisms of fire; they deserve to go home. Instead of a horrendous battle or a cluster of bombs, Kat is simply killed by a splinter bullet. An innocuous bullet meant for a different target. Paul's irony is that he dies alone when the eve of the German surrender. After all his trials, pain and misery he had become a soldier; he had become a man, only to die in the quiet of the western front.