It's actually 2.2 billion, not 773 Million. Troy (and thus the other media sites) just doesn't know or have the other 4 collections that were alongside collection 1.
While 2 factor logins is better than no 2FA, it's far from perfect. There are some mobile tricks to get peoples 2FA SMS messages and there are also some phishing tricks which have recently been made extremely simple that can be used to trick people in to authenticating with 2FA but you take over their session.
https://www.zdnet.com/article/new-to...at-bypass-2fa/