Edit: it is factually true to say Trump lied in manipulative ways constantly, and easy to confirm. This is not a partisan statement, it’s a fact that can be checked. Here are 5276 examples: https://projects.thestar.com/donald-trump-fact-check/
The issue here is that, as journalists, their job is to look at facts and weight evidence independently, rather than simply base judgements on the person making the statements. There has been ample evidence to at least consider a lab-leak theory very plausible, or even likely, but those were largely ignored. Instead, the media seemed content to report that Trump is claiming this thing, and Trump sucks, so this thing must also suck. Not exactly inspiring behavior from the "fourth estate".
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.