I’m not sure how much MFA would have mattered in this case.
23andme login is an email address. Most MFAs seem to use email as an option these days. If they’re already reusing passwords, the bad actor already has a password to use for their emails that’s likely going to work for the accounts that were affected. Would it have brought it down? Sure, but doesn’t seem like it would’ve been the silver bullet that everyone thinks it is.
For the grand majority of folks, Name, relationship label, self-reported location (city or zip), and birth year.
The ones with DNA compromises would be the ones whose accounts were directly accessed.