My opinion is that switch to daemonforums.org could happen before (actually it was bsdnexus.com).
My suspicion is that there has to be a threshold number of people for any forum to work & equally a threshold number of the right people. Recall that there was an outcry in March of people making ultimatums that there were just too much spam & that they were leaving. Some did.
Independently, there was a final push by the Moderators to control the level of spam seen by the masses. This tended to nullify any exodus, & many returned.
Ultimately, the Moderators saw that contact with Admin by myself & Carpetsmoker didn't result in any change, so the decision was made to abandon BSDForums altogether. The creation of DaemonForums was largely an independent set of decisions, but it did provide a focal point for the impending exodus.
Yes, leaving BSDForums could have happened earlier, but the resolve of that decision was not held by sufficient numbers or by the right people.
As stated elsewhere, it will be interesting to watch what happens with BSDForums. As the Admin there is out of the picture, how often does he actually visit the site, & at what point will he simply turn off the servers? Given that the spammers tend to congregate on specific subforae, unless one looks closely at the date of posts, it is not entirely obvious that there is virtually no new traffic. Note there are still new legitimate posts made by first-timers & others unaware of the recent drama. At this point, I tend to think that BSDForums will be available online for several more months. The Admin there will simply be paying hosting charges for no reason at all.