We've all been duped. I very much doubt their wealth has doubled, only that the numerical dollar value assigned to their wealth has doubled.
Governments and banks are printing and creating money. This just redistributes the existing wealth in society - taking it from people that have to work to pay the bills and giving it to people who's money comes from their (real) assets. Which rather handily defines the only two classes that count in this discussion: Wealthy and working.
Every year since the 1970s governments give everyone a 10% pay cut, recently this has been closer to 20 - 30% (which is why people are beginning to notice).
The trick to stopping people rioting on the streets is to give just enough to just enough people to make them think that every five years the value of their houses are doubling. Really the fact is that every five years the value of the money they earn is halving. The other trick is to publish official inflation figures that are a total fabrication of the truth. Better the voters are focused on house prices than daylight robbery.
Fun fact: In most years the US government's take from inflation is roughly the same as the amount they collect through income tax.