Why we make you turn on multi-factor sign-in
Multi-factor sign-in is the single cheapest thing you can do to stop an account takeover, and it is the one people push back on hardest. It adds about four seconds to your morning.
Almost every compromised mailbox we are called out to had a strong password and no second factor. The password was not guessed — it was reused somewhere else that got breached. A second factor makes that irrelevant.