Simple: don't show it.
More easily done by having Anakin Skywalker not be the main character, and occupy less of the focus. Neither would Obi-wan exclusively be the protagonist, so that the fight which leads to Vader's need for the suit of armour isn't really shown either. This allows Anakin to 'disappear' from the story, say at the end of Episode 2, without being fully explained; and Vader to appear as a menacing and mysterious villain who hunts down and destroys the Jedi in Episode 3.