If, I write IF, this is happening across the entire AdSense network then G are in big trouble
I may have got this completely wrong, in which case I will be told. Anyway, here are my thoughts. Google, I believe, runs AdSense and AdWords.
Just because AdSense publishers aren't doing so well, why should Google be in trouble? Google takes money from advertisers, and I assume that this money is taken up front.
Advertisers' money can be (and probably is) invested to make more money. AdSense publishers don't pay anything to Google, they just help empty Google's coffers because Google pays them.
Protecting advertisers and giving them the maximum ROI helps keep the money keep coming in. If advertisers are happy, they keep paying to advertise. Google is actively protecting advertisers by invalidating clicks that they don't believe will 'perform'. This must be good for advertisers and so they keep giving their business to Google. They now only pay for some, not all, clicks. This doesn't help AdSense publishers, but I guess it is of little significance to Google. Google hangs on to more of the advertising money by paying out less. I know that Google takes a cut of publishers' money but it is relatively small.
If publishers were doing really well, then advertisers budgets would be depleted a lot quicker. If they didn't think they were getting a decent ROI they would stop advertising with Google and that wouldn't be good for Google's business.
As I see it, with the same company managing advertisers and publishers there is a conflict of interest. If one group does well, the other suffers. If I was running a company I would protect whichever party paid me the money, in this case, advertisers.