I'm very interested on how this was done. I dont think I SEO my channel at all. And I did a quick test on my other test account (not so popular at all) which pulls in 0. I used http://www.prchecker.info/check_page_rank.php But when I add links to my other blogs and sites they get indexed fast. Anyways goooo youtube!! Youtube gives you wicked targeted traffic
someone possibly thought your channel was good enough to add backlinks to it and or blog about it. Great job on that!
Youtube is a Google company so this does not surprise me. Ive heard Google loves its own companies before.
Hope that PR carries good traffic too! Maybe what you've done was a good example of naturally built backlinks which Google prefer.
You might have received such a High PR for your channel, because of inter Linking. You see, users join in your channel and it appears in their profiles and so on