The first thing Trump said when he got elected was that his inaugural crowd size was bigger than Obama's.
The photos are there, the videos are there, you can see with your own eyes that Obama's crowd was bigger.
This is not some complex issue about some piece of paper that someone might/might not have faked but physical evidence you can see for yourself.
Yet Trump doubled down on this lie. That's what he is - a liar.
Of course there are lying schemers on the other side too but you cannot deny this fact.