> people jumping from the fact that there is a lab in Wuhan to the conclusion that it must have come from there

The Wuhan Institute of Virology is China's premier virology research lab, its first biosafety level 4 lab, and one of the very few (or only one?) that was doing gain-of-function research. Wuhan has a population of 12M, which is just under 1% of China's population.

The fact that the virus emerged there, of all places in China, is non-conclusive but highly suggestive circumstantial evidence.