No matter what the Sermons of his misled disciples say. Vivec drew his divinity from the Heart of Lokhan, he and Almalexia were the first to do the unthinkable, they forced Sotha Sil to join them, Voryn Dagoth prevented them from doing even worse, lest in their lust of power the Chimer might have shared the fate of the Dwemer. Thanks to the tragic sacrifice of our Lord Dagoth Ur, King Nerevar's most loyal friend, the conflict was stalled, until the Heart of the Lokhan could be destroyed and with it the divinity of the impostor gods. The prophecy of the Nerevarine was fulfilled, although with tragic consequences. And in the end Vivec even complied and accepted that time has come to pay for his sins.
Dagoth's tragic sacrifice? He accessed the heart unprotected and destroyed his mind in the process.
Vivec himself brands himself the Thief he knows he stole divinity from the heart, but that does not stopping him from realising his place the Godhead and the Godhead's place in him.
"He was not born a god. His destiny did not lead him to this crime. He chose this path of his own free will. He stole the godhood and murdered the Hortator."
He openly admits he killed Nerevar and stole Godhood and that he killed the emperor but that's for another time... For a mortal he seemed to do pretty well against Azura and he did so with CHIM, so he accessed divinity another way, as well as just stealing it.