Why is the normal operating airspeed so much lower than the cruise speed in this table?
You really answered your own question. Vne is based on IAS, the actual aerodynamic pressure at any given altitude and speed.  This is why the Mach number is included too, as approaching transsonic adds additional stresses to the airframe.

TAS, as mentioned in previous threads will be much higher than IAS at 35000 feet.  It is fun to enter speeds and altitudes into the TAS calculator to see how close one gets to Mach 1 at 250 IAS when you climb.

TAS is groundspeed without wind speed and direction factored in.  It is the actual aircraft airspeed relative to the airmass. Notice 480 is Max Cruise.