In the Star Wars universe, it is stated that slavery is a primary tool of the Sith—for controlling one another, and also for the subjugation of the entire galaxy. And thus it stands to reason that if Anakin is truly the Chosen One (and this is confirmed by Lucas’ canon), then he is also the one who is destined to destroy the Sith, and by doing so, it is implied, break this seemingly-perpetual cycle of slavery (and mental/ideological enslavement).
“This is why the climactic and emotionally cathartic ending of Return of the Jedi must herald an end to this cycle. What does destroying the Sith mean, if not that? Without this, there is little point to Anakin’s otherwise wholly tragic story. Without this, I would argue, there is little point to Luke’s story, either.”