I don't think there is anything to be amazed about, I think most Mac users are not very computer savvy, which is why they chose Mac OS in the first place, OSX has always been very user friendly.. Which is a good thing..
But that also means there will be a lot of users downloading and installing this..
Well, I am sure you can find same same amount of 'not very compter savvy' people on windows too. Honestly, it is just stupid to label people based on their preferred OS as 'computer savvy' or not. I am using computers (programming, build my own, ...) since almost 30 years and switched a few years back to Mac ... does this make me now not 'computer savvy' ???
I think the main problem is that Mac users up to know didn't have to worry about this **** and are not expecting it. Even technical people feel safe on the Mac (Though they might use more common sense than none technical people)