IBM was the main employer in Duchess County, NY. It eliminated and reduced its production to the extent Dutchess County's economy was decimated. The mid-century prosperity was gone.
Some time later NYC shuttered its vast network of psychiatric facilities and facilities for the developmentally disabled. The economy took a second nosedive.
Public sector compensation was slashed around this time as well.
Now where there used to be convenience stores, video rental stores, and mom and pop restaurants, there are payday loan outfits and pawn shops.
The real estate hasn't crashed. My best guess is people from the City view it as a bargain especially because the Metro-North commuter rail infrastructure still exists and remains fully operational.