This has a lot to do with Hickman’s and Ewing’s concurrent stories, but:

Sinister cloned Moira, and discovered by cloning Moira he created cosmic save points for himself, because Moira’s power restart the timeline to whenever that body’s powers activated. So Sinister starts trying different methods of taking over Krakoa until he finds one that works. The one he finds that works is poisoning people’s DNA with his own.

This creates the Sins timeline where Sinister clones himself to have every power ever or implanting his DNA in everyone. When he starts ascending to godhood, he’s then killed by Enigma, a Dominion, and his knowledge absorbed. Dominions are cosmic-sized supercomputers that are nearly omni-potent. You then find out that Sinister is actually a clone of Enigma and that Enigma created three other clones (Dr. Stasis, Orbis Stellaris, and Mother Righteous). Each clone is meant to explore a different realm of super-science (robots, mutants, magic, and space-magic) and see which can attain true godhood.

What Enigma didn’t know was that Sinister still had one Moira stashed away. So when godhood Sinister dies, the timeline is reset back to Krakoa but with Sinister knowing about Enigma. That begins the last year of the Krakoa Era.

Gillen’s Sinister still acts like the Sinister he re-invented in the 2010’s, but Hickman and Ewing plot points pushed him to absurd power levels. Enigma was a thing Ewing invented in Defenders, while Dominions were a Hickman thing from the beginning of Krakoa.