Who, exactly was Trump running against? And since when did we begin determining who is the rightful POTUS by the turnout for the inauguration?
And for relevance - Trump’s crowd was the largest turnout for a GOP inauguration on record.
(and never mind that DC and the surrounding area is overwhelmingly Democrat/Liberal - and FAR more inclined to turn out for a POTUS more matching of their position. Many of those attending Trump’s inauguration came from DC.
And then there is the little timing issue that others have mentioned.
Hillary had no one for her inauguration.