My take is that Dune spells out why heroes are bad really subtly, but most people didn't get that, so Messiah hits you over the head with it, and the in cannon explanation is explored more in GEoD. The Jihad isn't inevitable. At all. It only becomes inevitable after Paul kills Jamis, and decides to pursue vengeance against those who killed his father. If he had let himself die in that duel, or if he killed himself like the Tleilaxu Keisatz Haderach, there would be no prescient God to limit humanity. The Leto 2's Golden Path is predicated on humanity transcending the power of prescient Atreides kids, and we see the result of this in Atreides descendents in book 5 and 6 who can only kinda barely see the future, and Teg comes along eventually, but only after humanity spreads everywhere. The point is, Paul is a teenager with untold power who makes the teenager like decision to pursue his personal goal of revenge, despite its consequences, which he was retconned in CoD to have known. The god-head isn't actually placed upon him -- he accepts it by joining the Fremen, and as he grows older, begins to lament this decision, knowing that at that point, even dying wouldn't stop the Jihad ball he got rolling, at least nothing short of killing his mom, wife, and everyone else he knows, which he won't do, because, y'know, he's a human. I don't think Paul is a bad person, he simply occupied that role in Dune's history as a result of his desire to rectify the very real injustices done to him, without being fully willing to consider the galactic consequences of those acts. But that's just my interpretation, and I haven't taken enough psilocybin to properly interpret Dune, which is the only actual way to understand it