The only reason that Anakin joined the Emperor in the first place was because, whether or not Sidious/Palpatine was lying, he promised him that the darkside of the Force could save people's lives. Anakin had the Jedi arrest the traitorous Sith, he reported him to the Jedi, but in the end, succumbed because he was desperate to save padme from dying in childbirth, to luke and leia. He had premonitions, or visions, through dreams, that foresaw her dying from childbirth. If Vader was strong enough in the darkside, he could save her. Anakin became Vader before he got the iconic suit, it was a ceremonial name the emperor gave him. Whether or not it was a story that the emperor made up to tell anakin, or he told him the truth, anakin joined and believed him and helped him betray the jedi and republic, and did bad things, to get powerful enough to save Padme. Yet, Padme died in episode 3. After that, anakin, now darth vader and a cyborg, became the emperor's 2nd in command, ruled the galaxy as a sith for over 20 years, had the empire do evil things, like Alderaan and the death star for instance, and the events of the original trilogy happened, until he eventually betrayed his master and saved his son. Why did anakin stay with the empire/sith after Padme died? It doesn't make sense. He turns to the darkside for one specific goal, then, after that goal fails, he just stays in the evil state he was before. His original purpose for becoming evil was gone, and he failed at saving his wife, so why did he still serve as a sith for 20 years? It doesn't make any sense at all. Padme was gone, why not turn back to the light side, there's no point in saving her now. An interesting what if, is, if Padme lived in episode 3, would he have still stood by the Emperor's side for another 20-30 years or so? Did her death drive him to madness? Or, could she have brought him back sooner than Luke did if she lived?