fear is the mind killer

Duke Leto must take House Atreides to Arrakis, or be declared a traitor to the Imperium and hunted down. He knows it's a trap and that the Emperor is, in the very best case scenario, setting him and his family up for a serious reversal of their fortunes (far more likely, he's outright scheming to get them killed). But he doesn't have a choice. He must go to Arrakis. He does go to Arrakis. He dies.

Paul and Jessica must flee into the desert or the Harkonnen soldiers will kill them both brutally. They must go to the Fremen for refuge or the desert will kill them. They go. They find that the Fremen have already begun to mythologise Paul. He's the Mahdi, the Lisan al-Gaib. There is no option for Paul to be a normal person here. He is either the messiah or he is a false prophet, and false prophets in a nation of true believers don't live for long.

So Paul fits himself into the mold of the myth. He becomes Muad'dib and leads the Fremen in war because they believe too much in him to let him be anything less. Is it manipulation? Yes. But because the Bene Gesserit have been manipulating the Fremen for centuries, Paul has no choice but to continue it if he wants to live.

He sees the holy war at the end of every timeline by glimpses and he fights to avoid it. To avoid it, he becomes the Kwizatz Haderach and gains the ability to fully see timelines, and thereby he makes himself that much more of the Fremen messiah and brings himself one step closer to the holy war. Every choice he makes is a choice for survival and an attempt to avoid that war, the war he cannot escape because every step he makes along the path to survival is one more step towards the war. He has no more choice in what he becomes than his father had in whether or not he went to Arrakis.