If you go back to the time when they were invented, many semantic elements, like article or footer, didn't exist in HTML. People tried to find conventions and efforts like microformats were an attempt to standardize those when the best solution (updating the HTML standard) was difficult. In terms of timing, it's worth looking at the arc of Firefox, WHATWG, the advent of Safari and Chrome, and table use for layout.

Google was a driver in practice. Accessibility and better web experiences were important to those involved. The reality was that people interested in this area were at the bleeding edge. Many people still held onto tables for site layout and Flash was still a default option for some in the period when microformats emerged.