No doubt, someone did. But what does that have to do with anything? Someone worked for this wealth, as well.
Now why should wealth be taxed in proportion to accumulated assets, rather than on a standard basis? (This regime has an odd result: If guy x throws a $2 million party, that amount of money is no longer factored into his tax "bill." But if guy x buys a real estate for $2 million, that money does count toward the amount of property the government will confiscate from him.)
And why in the world does your proposal only affect households with more than $10 million?
True, that would be a bit of a weird result, but that spending should help the economy. $10 million seems like a reasonable value, that way no one can claim that they are forced to pay this tax on any reasonable amount of wealth, such as a house in the bay area.