Because interest rates went down in those countries as well? We're only just coming off the lowest rates ever in the UK. The Euro hasn't existed for long but record lows there too. Oz as well.
Why hasn't the same thing happened in Japan, which has tripled its money supply since 1990? House prices (and the price of everything else) has remained dead-ass flat. The difference is the have federal zoning rules that allow the supply of houses to meet the demand of houses.
Japan price to income ratio is bad but that speaks more to horrifically low wages.
They've also been more aggressive about taxing real estate investment (they leaned their lesson in the 80s) and their zoning laws aren't captured by local busybodies.
If a growing region is declining, I would expect building to be outpacing growth, or a cultural trend away from wanting to own (reduction in demand for purchasing despite growing population)
It's also worth mentioning that every developed nation has a heavy interest in the value of the dollar, because of trade with the US, petrodollars, etc.