That’s fair, but this isn’t an ordinary liar. If a known con artist is raving about his new youth serum, after being caught lying thousands and thousands of times in the last 4 years, it’s not inappropriate for the press to respond with “this known con artist has no evidence to support his claims” after a short glance - they are so busy dealing with the other 1000 recent lies that they don’t have time to investigate everything this person says in depth. The magnitude of the lies and manipulation was unheard of.
The fact is, you need to hear the story from somebody credible before it becomes worth investigating, otherwise we would still have journalists trying to uncover the alleged thousands of murders by immigrants kept secret by bizarre conspiracies (which, again, lacks evidence) - the claims have to come from somebody capable of basic truth telling.