I can't really think of a good reason for Q to delete the posts on greatawakening, and then open up the board for anyone to post on.
It's not like the act of deleting them there is actually "removing" them since they have already been copied to the archive (aggregator) sites.
I am thinking that it must be symbolic of something, I just can't understand what that is.
My best guess is Q closed up shop. Job is done, or at least that phase of it.
Q had admonished to copy/save everything. One of the posts near the end ...
Feb 18 2018 21:14:27 !UW.yye1fxoQ 108 CLEAN ACTION APPROVED. HIGHEST AUTHORITY.
And after that, presto, board was wiped nearly clean.