[deanhills]

But in fact they should think purely based on scientific evidences, and nothing else.

I think scientists do think that way.  But of course at present there is no scientific evidence.  Just scientific theories.  Some of the theories link SARS to Covid 19.  That Covid 19 was a product of a SARS virus laboratory experiment in China that went wrong.  I heard the theory from a public health epidemiologist who is a bio statistician.  Which was interesting to me.  As until I heard it from the public health epidemiologist direct, I thought it was just one of many conspiracy theories doing the rounds. Looks as though it is a theory that is presently looked at by scientists.  With evidence not found yet.