Carl is getting on in years, God love him.
And, not to put too fine a point on it, but he's kinda let things slip and slide a bit these last few years.
He's playing the "activist investor" card again. It's worked before and it might work this time.
He's taken a relatively small position in Apple and therefore presumes that he can dictate to Cook and company what's best for Icahn's share position.
If Apple would only use its cash hoard to buy up even more Apple shares, Carl's Apple stake would vastly appreciate! He's confident that the shares he's bought in the low 400's could go to $700!
That's the way of American capitalism today; Icahn brings utterly nothing to Apple, but fully believes that his billionaire status and reputation as a bully should dictate corporate strategy at the ailing computer giant.
Sooner or later a corporate board will find the balls to tell these "activist investor" types to go fuck themselves.
The sooner the better.