I think the benefits of two factor authentication are pretty obvious.

As another commenter said above, email security is crucial given the number of sites and services that rely on email for password resets.

I can't imagine switching to an email provider that didn't use 2FA for that very reason.

For example Podesta's emails would have never been accessed and sent to Wikileaks if he had been using it. Despite his password having been compromised. Not everyone uses this feature but those who do feel it is really important.

For me personally, my email is a kingpin of my online presence. Gaining access to my email would provide overridable access to a good portion of my online accounts. Not to mention if my email was hacked by a bad actor, my identity could easily be stolen with all the emails I keep in my archives.

A motivation to Migadu as a service would be the ability to attract more enterprise customers. I know that at my company, MFA is required for all email accounts. Offering MFA would be very attractive to companies wanting to move their email over to Migadu.

Just support federation from something like Okta and 2fa is taken care of