Judaic interpretation, HD. Sorry. By that "logic" one would intentionally let his children fail so as to give them the opportunity to learn, through successive generations of death and destruction, how to appreciate what their forefathers had. It's absurd. If this is what reformed theology teaches, then it's absurd.
God created the angels knowing that He would throw out some of them
That is also absurd, HD. God created the angels knowing that some will fall away from Him on their own free will. But, if you follow Judaism and not Gospels, then you can surmise that angels cannot rebel against God— because they were created as obligate servants, so the only conclusion one can come up with is that God specifically created some angels to be discarded for no reason whatsoever! Absurd. Nothing short of absurd.
Well, that's what happened. Pretty much like why God planted the tree in the Garden. You can make up all sorts of things but them's the facts.
Otherwise you're into Open Theism.