The Zagat acquisition was not driven by Marissa, but another exec at Google Travel. When he was turfed out, that signaled the end for Zagat as well.
Not to mention: I was there when she stood up and told us how she'd made the acquisition. I don't know who your information comes from, but stop listening to them.
"On September 8, 2011, the company was acquired by Google for more than $150 million, the 10th largest acquisition by Google as of that date, at the championing of Marissa Mayer, its Vice President of Local, Maps, and Location Services."
She introduced Tim and Nina and took full credit for it. If your point is that she must have gotten the OK from Larry, Sergey, and Eric -- no argument. Any big initiative has some champion, who depends on top management approval. That doesn't mean that the CEO is personally the driver of everything.
It would not have happened had she not pushed it. If you can't accept that, then we'll just have to call this discussion Done. I was there; you weren't.