The main problem was and has always been that his lies travel faster and farther than the truth. It doesn't matter if Trump's statements are debunked. The original word is still echoing around the internet, being believed by credulous people creating a self-reinforcing cycle of disinformation. The media is complacent in this cycle by publishing the original lie before "fact-checking" it. When the lie is on the front page or the headline of a news show, but the fact that it is incorrect is hidden fifty pages in or on a crawl at the bottom of the screen, it does no good.