As I’ve been reading Matthew Stover’s ‘Shatterpoint’ I’ve been getting the impression Mace Windu is may possibly be the optimistic and very original form of Darth Vader. Born as him, raised and taught in the constructive senses by the Jedi order and Yoda and translated into Windu.
So, I have the belief when Palpatine strikes Mace in ROTS with his lightening, He literally sucks the life out of him onto himself and so when Anakin is getting medically repaired after the duel with Obi-Wan, Palpatine took that life energy from himself that he acquired from Mace and perhaps Padme when she was dying, and onto Anakin to have him stay alive. Palpatine really did create and restored life.
To add on top of that Anakin doesn’t turn into Vader specifically rather He turns into somewhat much of a lobotomized subject/voodoo zombie. How I think he rolled into this specific state can be called back to when Obi-wan said in SW77 of the Force having a strong influence on the weak-minded, as when Anakin imposed his fury onto Mace, Palpatine slipped into his mind whilst he was preoccupied and mentally swinged, ether intentionally or unintentionally mind tricking him into this psychological space.
it is not until he’s on his desolated birth bed, Anakin actually turns into the twisted sinister persona that is known as ‘Darth Vader’.