I feel sorry for Bernie, for him being mugged. I am sure these idiots who did this knew who he is, and they probably thought he would be carrying around shitloads of values.
This just goes to show how clever he is. The way he appears in the media, he seems like an arrogant, greedy, old man. Though I assume he is a really good guy. The thing is that when everybody thinks he is an idiot, the guys who actually know him will describe him as a good guy. This combined with the amount of power he has, makes him intimidating to some, and respected by everybody.
He is not able to hide his big wealth, so naturally people will target him in robberies. He knows this and therefore dont carry around expensive things.