Stupid people (Trump team) sometimes say smart things... Navarro is right, for the same reason 100 nations recently signed a petition at WHO asking for an independent investigation into how the Covid-19 virus was introduced into the world. One hundred countries, including sometime China ally Russia, can't all be wrong?
Keep in mind a lab created virus, a natural virus found in a lab animal, and a natural virus found in the wild all look the same, or rather, it's a matter of opinion as to whether the virus is natural or artificial. DNA, unless it's from a known cataloged organism, does not clearly show just by looking at the sequence whether it's artificial or natural.
The path of least resistance is to say China was negligent in warning the world about the virus (whether it's natural or artificial), and that's the path most countries and Trump's team are taking.
What would it take to change my mind? Find the Covid-19 virus in the wild, in a so-called "intermediate host". So far, unlike SARS, MERS, Ebola, etc, they've not done that. With most other viruses the intermediate host was immediately found, but not with C-19 (Ebola took a while too, but I would argue that outside of people living in Africa, nobody cared much about Ebola and was not spending money to research it that much; notice that once Ebola started spreading and got world attention, they luckily found a vaccine within a couple of years, since it had the potential to infect the world).