You can make a (stretch) claim at correlation just like you did, sure. But correlation (stretch or otherwise) is not the same as causation.
Additionally, in print media, subscriber revenue surpassing advertiser revenue is huge and not something that would be likely to happen without a successful digital product for a couple reasons.
Beyond that, yes, there's nothing here but correlation. However I think there is enough in the first two paragraphs to make a case.