Requiring a birth certificate wasn't actually required. Many states, however, did see lawmakers (primary Republicans) updating their laws around 2010 to require presidential candidates to provide birth certificates:
en.wikipedia.org
But whether one was provided or not wasn't the point. The fact that it became a public spectacle is. Do you honestly recall birth certificates being a relevant topic in a political campaign before Obama became a candidate? Hell, the issue came up again for Kamala - and by Trump, of course:
The US president fuels a fringe idea, echoing his past baseless claims about Barack Obama's origins.
www.bbc.com