Turntable isolation

I have read multiple references to the benefits of putting maple platforms under a turntable to isolate it from vibration. I have a question about why that works. Specifically, I have a VPI Prime that weighs 32 pounds. My Prime sits on a sturdy audio rack which, in turn, sits on a solid floor. It seems pretty well isolated. Would the addition of a maple platform or something like the IsoAcoustics Delos help in this situation?  Is the theory that the more weight I put under my turntable the better the sound?  If so, how, in a specific system, does one figure out how much weight is best?

Thanks for your help!