How? Hes an out and out psycho, an intergalactic Gobbels!
My theory: In EP3 we find out that Vader/Anakin rather than bring the balance back to the force, tips it on its head. With the Jedi dead and the Sith in charge of the galaxy, the Sith has complete domination.
No 'balance' its all one extreme to another, good or evil.
Theory:I feel that this great upheaval is what truly tips up the balance of the force. The one they sence in Anakin who can restore the balance isnt Anakin; but his offpring aka Luke and Leia.
and as to why the Jedi didnt see this directly, Yoda did say the dark side clouds everything.
__________________ Food is the path to the fat side. Pizza lead to flab, flab leads to blubber and blubber leads to rubber tyres.
Anakin did end the sith reign by killing the emperor only he did it as Vader, but by doing so he restore the balance of the force..................go figure