Unless you work at Google, the only thing anyone here can do is speculate. Even if your favorite expert drops by, he/she has zero clue as well.
I think the better question is: How is revenue affected by the ranking?
Most people won't say this but successful blogs don't rely on the rankings of 'X' search engine. If your blog has an established audience, nothing else matters.
Would you want a blog that ranks on the first page or a blog with 1000 loyal readers?
Those 1000 readers are worth far more than the quest to dominate rankings.
Finally, you said it was happening to many well established blogs but you didn't list any. Again, if it's a 'well established' blog, the owner(s) probably care less about the rankings and more about their audience.
This is the way you should analyze a blog rather than worrying too much about ranking.