Why do Shi’a Muslims believe predestination means humans don’t have free will?

Shi’a Muslims believe predestination means humans don’t have free will because God’s creation of mankind influences Muslims to act according to his will. God’s creation of mankind means God knows humans better than they know themselves, the quote from the Quran, “We create man, we are closer to him than his jugular vein” infers Allah literally knows humans better than their own anatomy, so he knows what is best for them - following his plan and acting morally correct in Islam. And as they trust God knows what is best for them, Shi’a Muslims would act morally correct and follow Allah’s plan which removes the possibility of acting otherwise and therefore their free will