Sure, but looking at their historic revenue, you're going from ~1.8B between 2007 - 2009 down to ~1.1B 2011-present[1]. In fact, their latest quarter for Mar 2016 only netted them 1.08B.
This is a ton of money and I reckon they could last a long time on it, but I believe the investor-mindset is something like "if you're not growing, you're dying" and if you're dying, you should probably sell at your peak. Looking at Yahoo revenue, it's clear they're dying and as a result, I wouldn't paint this as just greedy investors being greedy.