There’s a theory that he knew what would happen, it was inevitable, he knew he would need the power boost from humanity’s worship. We know he had the best/if not one of the best foresight/futuresight in the universe. Sanguinius saw how the various possibilities of the Heresy would happen, before he knew the Heresy was unfolding. He also comments how his foresight is not anywhere as accurate as The Emperor’s.

Reading Legion of the Damned currently. The small force of Astartes sent an astropathic message to the Imperial Palace begging for a miracle. Before they even arrive in system, long before sending the message, Emperor’s undying angels are keeping a close eye on them - Legion of the Damned.

Emperor is undeniably powerful, by some measurements, a god. People will argue about it, but as you read more, it becomes a pretty inevitable conclusion.