China's a communist nation. Anything that makes their government look bad is a problem for them. This is the same reason they silenced doctors who first were noticing new cases of coronavirus back in December and why they chose to exile journalists from the country. They don't want the true number of cases getting out.
How come China handled situation much better than Italy and USA which both had several weeks to prepare for the epidemic but the rate of spreading is faster than in China despite smaller population. Trump is just pointing fingers because he realized that situation in his own country went out of control and now he needs someone to blame.
China literally closed their citizens to their homes until the virus stopped spreading, while most of USA is still not under quarantine and virus is spreading freely and situation is getting worse and worse.