The prophecy was that the chosen one would bring balance to the force. With the Jedi in power, the balance was in their favor. By joining the dark side and slaughtering the Jedi, he brought the balance into the power of the two existing Sith. By killing the Emperor and dying himself he brought balance - neither existing. While one can assume the Jedi interpreted the prophecy incorrectly, one could also assume that they were just as aware of their obliviousness as anyone else. The dark side clouds all, and the dark side would defintely be clouding this. All the same, in the years of the prophecys existence (which, I’m unaware of who or when this prophecy was conjured), given Yoda’s attitude throughout, that even if the prophecy was misinterpreted by them, there was certainly more to it than what appeared. And if it was going to happen, then it will happen, most certainly a Jedi approach if I’ve ever heard one. Another Jedi thought is that there is always a choice, and yes, Anakin saw what Palpatine truley was and chose him over Windu anyway.
The philosophical meaning strikes me as somewhere between evil must exist for good to be relevent, and that one can’t exist without the other. Why this is just occuring to anybody is beyond me.

