Of one thing we may all be certain, it is not Donald Trump's fault. It is never the fault of Donald J. Trump. Even though the possibly criminal behavior of Flynn occurred AFTER he was fired by Obama, and even though White House officials, themselves, have to go to a Federal agency, not the White House, to get security clearances, Obama was responsible for Flynn having security clearance.
Since Gen. Flynn was involved in U.S. intelligence work during the Bush Administration, he received his first security clearances during that Administration. Republicans, however, reject any responsibility, by the Bush Administration, for vetting, on the grounds that while security clearance is by authorized agencies, vetting is the responsibility of the Oval Office. When asked, then, why should Obama be responsible for Trump not having vetted Flynn when Trump hired him, Republicans make a vague referral to Obama's special status.