I am of the opinion that Ms. Mayer was hired partly as a way for Yahoo's investors to hedge their bets [1]. Its a bit of a dark view on silicon valley culture, perhaps, but I think a valid one.

Anyways, I agree with your point that Yahoo had already suffered most of its damage. In many ways, its latest CEO did the best that could be expected of anyone in that position.

[1]:https://en.wikipedia.org/wiki/Glass_cliff