Our proof is the Qur'anBefore Muhammad Mani was referred to as the “seal of the prophets”
This term was understood as being one with the Bible prophets before him.
It was a statement of legitimacy
Many people claimed to be prophets back then.
It was a hustle.
The historical “Muhammad” was probably no different
Being successful at war and gaining followers doesn’t automatically make you a “prophet” or the “last prophet”
And calling yourself the “last prophet” isn’t possible logically. Where’s the proof?
Muslims gave him that title well after he died to legitimize the religion
And anyways if Mani was the “seal of prophets” (meaning the final one) and he came hundreds of years before Muhammad then that means logically Muhammad couldn’t have also been the “seal of prophets” and wouldn’t have used that title.
Unless of course the Muhammad legend absorbed aspects of Manichean teachings/beliefs and made its way into the Quran/Hadiths hundreds of years later after people forgot about Mani
But my job isnt to convince you. You already have your mind made up.
Go visit Mecca and Medina. Go to his grave.