Why is it that Trump's cronies Flynn, Manafort, Kushner, Session

Cape May Point - Why is it that Trump's cronies Flynn, Manafort, Kushner, Sessions, and now Donald Jr. can't remember meeting with Russians until stories break in the New York Times and Washington Post? On the Russia side of things, Trump's people were meeting with ambassadors, bankers, and lawyers both during the campaign and after he was elected - all with direct connections to Putin and the Kremlin. If there was no collusion or assistance from Russia, why is the Trump team hiding and being non-transparent about all these meetings and associations with Russians?