I mean, hmmmmm the first thing the nazi Stroheim does is trick a young boy and slaughter his entire village and made him think it was his fault in order to revive an ancient vampire with their blood. American JoJo and Italian Zeppelli being buddy buddy with an unrepentant and enthusiastic SS Colonel is simply realistic to me.

You're right in that he softened Stroheim over the course of the manga to make him more relatable so you could root for him when he's trying to stop Kars with JoJo and then had him die valiantly in Stalingrad like some sort of hero