Hard to know how many National people voted for Labour to keep the Greens out, I am sure quite a few did but it doesnt explain the massive shift in favour of Labour IMO. I think Jacindas popularity had something to do with it plus in these uncertain times I think people tend to want some consistency in their lives and voting Labour back in may have given them a sense of security. But who would know, we will just have to see how things pan out.