If Marissa Meyer orders everyone to work from home, then that can be attributed to her. She can take credit for that. It was her action. But if the stock price goes up $5 today, there's no way to show it was a result of ordering everyone to work from home. If you want to make the argument that Meyers actions led to 33b in market cap growth then make that argument. What did Meyer personally do that caused the growth in market cap, and how?
Consider: the CEO of Ford decides Ford will no longer sell petrol based cars (getting the board to go along with it too) and then executes that strategy.
If it succeeds then the market cap of Ford will increase. If it fails then it will decrease.
On the flip side, no matter how clean a janitor can make the facilities, he can't dictate corporate strategy and Wall Street doesn't care how clean Ford's bathrooms are.
This doesn't diminish the importance of a good janitor, but let's be honest about the limits of their impact.
"Yahoo stock was up by 8.5% at the time of writing." http://www.businessinsider.com/yahoo-verizon-sale-approved-2...