According to the NY Times, “President Trump was informed weeks ago that his national security adviser, Michael T. Flynn, had not told the truth about his interactions with Russia’s ambassador and asked for Mr. Flynn’s resignation after concluding he could not be trusted, the White House said on Tuesday.”
So it took weeks to conclude that the liar could not be trusted. What exactly were they looking for in the intervening weeks? The ability to cover it up? That’s the best I’ve got.