The forum is based on an older version of SMF (specifically, 1.1.19 as can be seen in the bottom center of your screen). A new version of the forum has been in development for quite some time now, and it would be a waste of resources to implement 2FA here now. This is the link to the
Beta version of the new forum, alternatively you can follow
the development here.
I'd say that a good part of those accounts get hacked due to the leak during the previous forum hack (as some have no changed their passwords and whatnot).