I saw those ‘before - after’ pictures too, and it was pretty obvious that the slide area had slud (slidden?) several times before. If any pile of dirt was just itching to slide again, that was it. So take yr pick: Socialist government shoulda banned building houses downhill, or Libertarian gov’t shoulda said “tough luck suckers, we ain’t gonna dig you out.”
OK, more seriously, I wonder how the insurance companies rated that development area.