They locked everyone down. After trying to hide the pandemic and failing (see https://www.latimes.com/world-nation/story/2020-02-06/coronavirus-china-xi-li-wen

They locked everyone down. After trying to hide the pandemic and failing (see https://www.latimes.com/world-nation/story/2020-02-06/coronavirus-china-xi-li-wenliang https://www.latimes.com/world-nation/story/2020-02-06/corona...). If everyone's locked down and the CCP is doing all the counting, how are you going to know anything other than what you're told? Undercounting is a lot easier than trying to hide it, which again, they did until they couldn't. The presence of foreign ambassadors and business people means nothing. They weren't involved in auditing data collection.