Future Zamas was once a Supreme Kai apprentice training under the Supreme Kai, Future Gowasu. For unknown reasons, Zamas always held a grudge against all mortals and humanity in general in which Gowasu hoped Zamas will eventually get over someday.
One day, when serving Future Gowasu tea, he found his master killed under the hands of a mysterious man. The stranger then reveals himself to be Zamas, from another timeline. He had come here looking for a timeline and universe without a God of Destruction, as Supreme Kais are not allowed to lay a finger on the planets. His search through all reality eventually brought him to Future Zamas's world where Universe 7's Destroyer, Future Beerus was deceased. Zamas offers Future Zamas a new opportunity to begin the "justice" the world deserves, in which Future Zamas agrees to. The two then gathered the Super Dragon Balls and wished for immortality for Future Zamas then destroying the Super Dragon Balls so no one could revert their wishes.
With no one standing in their way, Zamas and Future Zamas then initiated their plan: to kill "unnecessary" mortals in order to bring "justice" and to create a "utopia" in the future timeline, as well as any other timeline with it. After killing all of the Supreme Kais, and thus by extension the Gods of Destruction, Zamas unleashed his wrath on countless planets, killing as many mortals as possible while Future Zamas stood back, watching their plan unfold.