Most people are assuming this is a post-Missy Master but he seems closer to the Simm master (unhinged and quick to temper) whereas Missy was more poised and calculating. Plus that way it doesn't undermine Missy's arc. That's what I choose to assume until told otherwise.
I finally watched Part 2 and I'ma hit you with some logic for my theory.
This episode introduced a concept that could give the Master a very compelling desire to forget and move on from something.
So I think the order is Delgado - Pratt - Beevers - Ainley - Roberts
Then Dhawan, who finds out about the Timeless Child and massacres Gallifrey. Eventually coming to terms with what he does and wanting to forget, the Doctor/himself helps by equipping him by using a biodata module and a chameleon arch in conjunction with a fob watch and putting the Master somewhere in the past where he can live out a relatively full human life of solitude and safety, using his TARDIS to heavily manipulate his memories.
Then of course Jacobi - Simm - Gomez.
Yana specifically says he was "found with it, an orphan in the storm, a naked child found on the coast of the silver devastation, abandoned with only this".
And after the Master massacred all of Gallifrey, he could use the reminder that even though he killed all of them, he didn't kill 1, and that "you are not alone".
e:
Obv. just talking actors here tho, since those aren't his exact regenerations since the Master does a lot of body snatching, but yeah!
