Why are so many people think masks work against the China virus?

You mean the TRUMP virus.

Duh...because it does. 

You jerk and a handful of racists are still believed: the world is flat, covid19 came from China...and 

Trumpo won the election.

https://nationalpost.com/news/world/coronavirus-si...

If masks were ineffective, I would expect people like barbers and nail technicians to be dropping like flies. Since they are not, I think masks must do something. 

Masks are in violation of the second amendment. The scrutiny on a free state we the people have the right to relijin and gunz without wearing masts will not be impinged.

Chrump fo' EVAH!!

doctors say so........................................................

Counties in Kansas with a mask mandate saw a 6% decrease in covid cases.  Counties that didn't have a mask mandate saw a 100% increase.

Seems pretty simple to me. 

The scientific medical evidence is that a suitable mask, properly worn will very significantly reduce the probability of an infected wearer spreading coronavirus to others.

You need to learn the difference between "works" and ineffective.

Most masks are ineffective.

Almost all masks filter at least 4% of small aerosol particles 

And California's 267% increase in covid cases in Nov shows that "places where people wear masks have a lot fewer cases" is not true.

Places where people wear masks have a lot fewer covid 19 infections. Mind you, everywhere has a lower proportion of covid cases per 100 000 people, than the US.