NOVI PETRIVTSI, Ukraine—After President Viktor Yanukovych fled his mansion here last year, activist Oleksandr Aronets crawled through the ventilation shaft and photographed the opulent objects he left behind: a Steinway piano, a Reuge music box, a carved mammoth tusk.

Lying on a shelf in one of his rooms was a life-size, golden ornament in the shape of a loaf of bread. It wasn’t the most extravagant object, but it was shaped like the most-ordinary, Soviet-style bread—and it became a symbol of the corruption of the runaway...