The Reagan White House moved to lower tax rates for developers in the 1980s and then years of low interest rates glutted downtowns with office buildings. Time's up.
In the middle of the 20th century there was a huge migration of people out of city centres and into suburbs. Some of my relatives bought up properties back then and made bank when the city expanded. I don't expect inner cities to remain quiet forever, but the way they're used might change.
White people. Because due to desegregation, they were suddenly required to have black people in their neighborhoods if those black people wanted to buy a house there. So they ran away from the black people.
Not everyone lives in the US. While aboriginal people in Australia also tended to stay in the inner city they make up a much smaller proportion of the population, and the divide between city and suburbs was more along socioeconomic lines than racial ones; it just happened that due to racism the Aboriginals were in the lower socioeconomic group.