If I were to speculate, it has probably been in the works for months now. G+ changed leadership back in April, and the winds probably changed direction with it.
Edited to add: Yonatan also mentions in a comment on the official post that "Vic was 100% involved in the process and approved the whole thing months ago." I can vouch that this is the truth.
It's still possible to change your mind. Also, some things to consider: (a) Yonatan is the tech lead for G+. This is something he would be an authority on. (b) I also work for Google, have no particular reason to be loyal to Vic [I've opposed the names policy from the start], and I'm also willing to vouch that Vic approved it.
So if you still don't think that's enough to believe it, well, that's your prerogative, but I doubt anything is going to convince you in that case.
Vic has been particularly offensive about this. The restaurant analogy comes to mind. He also stonewalled for a long time, was kind of a dick about it, and refused to budge when presented with evidence. If something magically made him change his mind, I would love to know what it was.
That said, do you know what evidence made Vic push the names policy in the first place?
I don't think anything "magically" changed it - more just it evolved over time. See the quote from Yonatan I posted elsewhere in this thread regarding the original motivations and successes or lack thereof.
Surely there were discussions which lead to the names policy, as well as more discussions that lead to the repeal of it?
I have a hard time believing that a single person at Google (Vic) would be given so much free reign to make policy changes based on how it "felt" without having a shred of evidence. Unless I'm misunderstanding?
Total guess: Google wanted a world where Google could sell real, identifiable people to advertisers. Not enough real, identifiable people came to the restaurant.
At this point I doubt a name free-for-all is going to swell the occupancy.
[1] http://bigstory.ap.org/article/googles-top-social-networking...