When you are incompetent and made mistakes as a government official, what do you need to do to keep your approval? Gloss over the mistakes and blame them all on other countries, as Trump's administration has shown us.
In order to pass the buck of their incompetent handling of the pandemic, Washington has become passionate about peddling conspiracy theories about China, claiming they have evidence, yet it hasn't revealed any to the public.
But does it really matter to them whether they have solid proof?