They tore down a chunk of CBR and built Riviera (DVC). Poly, Copper Creek and Grand Fla all re-purposed existing rooms from cash side to DVC. When was the last all cash hotel built? Somewhere in this thread (I tried to find it) a person showed how there is less hotel room nights available than 5 or 10 yrs ago (sorry dont recall exactly). So, Disney has constrained the supply of cash rooms by focusing on DVC.
He/she also showed that attendance is mostly flat over last few years. (Based on Disney's 2018 annual report WDW seen ~4% increase in attendance so I am not sure the long term trend). Leads me to believe cash room demand is constant or even up a little, while cash room supply is down. This is what is causing prices to go up at the higher end resorts like Poly, Grand Fla etc. As the higher end resorts 'price people out', this increases demand for the mods and values, pushing their prices higher.
DVC has always had higher occupancy rates than cash. Instead of lowering cash room prices to increase occupancy they have chosen to remove supply instead. They are leaning on the DVC side to continue filling the rooms.