What exactly happens during the sourdough ripening?
Here is a small piece of the answer. https://pubmed.ncbi.nlm.nih.gov/33496265/
It is not just yeast strains but especially lactobacillus bacteria that develops and helps to change the ph of the starter. This change in ph is what helps the sourdough bread retain moisture and results in the creation of acetic and lactic acids which create the tanginess.