Arthas, Sylvanas and the nature of self
Credit to ARM3481 on the Scrolls of Lore discord for the following analysis: Admittedly in-universe it makes sense for the world to continue blaming Arthas, so from that context it's not hard to understand why some people just latch onto that incomplete view of things. Especially depending upon their experience playing and familiarity with his pre-WoW development. But really from an informed "reader" PoV, you're correct that while it's Arthas' fault for things getting to the point that he picked up Frostmourne, after that choice he's basically no longer that Arthas any more. The creature he became at that point was the worst of himself magnified by the influence of Frostmourne, which then became even further removed from his old self once he deliberately extracted whatever lingering vestiges of his humanity remained after his battle with Illidan. Arguably the Arthas that went to the Maw would be whatever was left by his death at the end of WotLK, which m...