Remember, 70k 'users' actually means 70k accounts sub'd.
It does 'not' mean 70k concurrent connections - or even 7k
More likely, Voat (or here) will see an influx of ~250 to 1k concurrent users, a majority of them will be lurkers, not posters.
It's bad - don't get me wrong, I'm not trying to suggest it is not - but it's not catastrophic, to accept in users.
Besides, lets be honest, some won't bother to go anywhere but twatter or fb. Some will come here. some will head to /pol/ (poor cucks) and some will head over to voat/gab/etc.