Facebook is not what pushed everyone away, it was how often the site crashed, then to add toppings, the worst crash (or server cut off?) when several years of data was lost.
The forum was always better than FB, but the site going down all the time pushed people away.
Now there is 1,904,304 different SQ groups on FB from everyone making their own groups (typically after being banned from one) and I doubt you will get anyone to return at this point due to the simplicity of just using FB vs a forum.