Yeah, but that wasn't what I was talking about. The characters don't matter to Strahd, because his existence and goals and personality and suchlike are entirely independent (the same for any set of characters).If Strahd was dependent on the characters present, then a different set of characters would not have Strahd -- he's dependent on the first set.
The reason characters don't matter to the AP is because defeating Strahd is the only way to successfully complete the adventure, and because there's really only one path to defeating him. In principle, one could have a different set of characters figure out either an entirely different way to complete the AP or an entirely different path to defeating (or, perhaps, otherwise confounding) Strahd, and in such a case the characters might matter to the adventure but not to Strahd.
That might not make sense, or you might not agree with it.