It's Newtons laws of motion.
When wind hits a turnine blade it moves the turbine from the energy transfer. The wind doesn't continue along, it has lost its movement.
Eventually the air will be still everywhere, your windmill will be worthless, and the gentle breeze you took for granted will be gone forever.
Those run 24/7 and I can already tell how bad it is. In the 80s the wind was much stronger.(Edited 23 seconds later.)