The Impossibility of Knowing How Much Money Is in Banks

How do we know that the feudal aristocracy was overthrown by a series of revolutions and that they no longer exist as Marx and Engels claimed? There is no way to tell. How can we know whether Elon Musk or anybody else is the richest man in the world, or how much money anybody has? And so I think that's the point, who are aristocrats they go broke, you know, and they have no money that's the era of the common man.