Don’t forget the brass container. Brass is an alloy of copper and zinc, both of which have antimicrobial properties. All those acids, brewing in a brass container for several days, would mean a significant amount of metal leached into the brew.
I doubt a significant amount leached, but surface contact alone would be a potent antiseptic.
“Brasses demonstrate bactericidal efficacies, but within a somewhat longer time frame than pure copper. All nine brasses tested were almost completely bactericidal (over 99.9% kill rate) at 20°C (68°F) within 60–270 minutes.”