Why not, even if Marissa Mayer managed to moderately slow the decline of a major company, the fact that it still collapsed certainly isn't the sort of deliverable that justifies 260M$.
I believe Yahoo was in real trouble when Marissa Mayer was hired and there are some decisions she made that were clearly wrong in hindsight. I don't feel qualified to judge her performance in detail but 260M$ is a glowing endorsement which seems entirely disconnected from the reality of what happened during her tenure.
There is an article out there that talks about her repeatedly being hours late for meetings with major CEOs. There were lots of other negatives. It made her sound like a first class train wreck.
If the article is factual she was compensated $260M for turning in a performance that could have gotten a minimum wage grocery bagger fired several times each month.
This is just a demonstration of the different worlds we live in. There are countless examples of CEOs getting sacked for gross mismanagement and then rehired in a new executive role. Unlike other time periods it's easier (not easy) for people to enter that strata of society but once you're in it seems like you're set for life and the worst that can happen is you get setup with a cushy job with generous paycheck to basically not cause any more trouble.
I believe Yahoo was in real trouble when Marissa Mayer was hired and there are some decisions she made that were clearly wrong in hindsight. I don't feel qualified to judge her performance in detail but 260M$ is a glowing endorsement which seems entirely disconnected from the reality of what happened during her tenure.