"Why can China build a hospital in 10 days?"
They can't. They can put together pre-fabricated modules into a minimal-care, temporary structure in ten days. The US Military has been doing it since Vietnam. Also, this so-called "hospital" they have erected has no testing facilities, no X-Ray lab, no MRI center, and no surgical ward. Footage has shown it is a lockdown unit, prison style, with nothing but individual, bare, two-person rooms that lock from the outside. It's a place to take the dying where they will be locked away until they are cremated.
Also, from personal experience in China's barbaric, primitive, backward healthcare system, I can attest that those who go in would be safer staying at home and dying in comfort, rather than dying in the care of the butchers China laughably calls "doctors."