Jake Tapper reports that it was pressure from Obama that caused Mubarak to give up and leave.
I have no idea whether that’s true or not. My guess is that it’s not the real reason, and that the real reason was that the army decided the civil unrest was growing too threatening and told Mubarak to skedaddle or else.
But I will make this prediction: if Egypt turns out badly, Obama will deny any role. And if it turns out well, he will take the credit.