He found out later that he was wrong...that the staff was behind POTUS.
According to this scenario, Rosenstein, finding himself way out on a limb and all alone, began to backtrack.
If this story is accurate (and it well may not be), Rosenstein has been exposed and will either be used as bait to hook bigger fish...or he will be permitted to retire.
Or maybe the story was fake but the news was real?
Maybe things are coming to a head right before the midterms? Some say Trump plays the long game. I have no clue if RR is in on the game or is going to be asked to resign.