There was a lot of evidence supporting the wet market theory at the time and supporting that it wasn't made in a lab (https://www.nature.com/articles/s41591-020-0820-9) including exposure to the market by early patients (https://www.thelancet.com/journals/lancet/article/PIIS0140-6...) and the fact that wet markets have been guilty of spreading similar diseases in the past (https://pubmed.ncbi.nlm.nih.gov/14738798/)