What changed? Many years ago, ads were very bad. Then Google got into the business and enforced clean, tasteful ads and things were good for quite some time. B

What changed? Many years ago, ads were very bad. Then Google got into the business and enforced clean, tasteful ads and things were good for quite some time. But then they started deteriorating again, worse every year until I finally installed adblock early this year. Did something cause the power balance to swing back away from Google or something? If so, what?