After hearing "Darth Plagueis" in Revenge of the Sith, I've always thought about who he was and what influence he really had on the galaxy.
We first hear his name in Episode 3, when Palpatine is using the story of Plagueis to bait Anakin Skywalker to the Dark Side. Palpatine knew Anakin was created from midi chlorians due to the work of Plagueis, we also know that Palpatine killed his former sith master in his sleep, letting Plagueis know that he let him use him so he could get to where he was, Surpeme Chancellor and ultimately Emperor. Palpatine did all this during Episode 1, that is probably why Yoda could not see Anakins future when Qui Jon Ginn brought him infront of the Jedi Council.
The powerful Skywalker Bloodline.
Now if Darth Plagueis is as powerful as it is said, how could someone like that truly die in his sleep after years and years of mastering the manipulation of midi chlorians? After declaring end to the rule of 2? You don't get the name "The Wise" from being foolish or naive. I believe he saw his dooming fate from the hands of his apprentice and let Palpateine carry out his plan, knowing that the Skywalker bloodline would still be available years later. Maybe he even foresaw Luke Skywalker convincing his father Anakin back to the light. Knowing it would be easier to turn someone further down the line, why not come back years later to have a second chance at being all powerful? If you create something you always want to play with it and I believe Darth Plagueis is doing that with Anakin's grandson, Kylo Ren, being Supreme Leader Snoke.