What the *#$@ happened??

Could you tell us which woods you are taling about? Also, what table is that?
Generally speaking, it is not simple with woods. Maple is the most popular, I never heard anyone use ebony or ironwood, as an example.
You probably got a lot of vibration energy reflected back into your analog rig, among other possible factors.

Wood is 3" maple, TT is a ClearAudio Concept. Previous wood was just laminated pb, hence my surprise with the depletion of stage depth.

I am surprised too. I have 3" maple block under my Nottingham Spacedeck and everything is fine.

All vibration control devices are "tuning" devices--the fact that they alter the sound means that they can alter the sound for worse result.  Some people think that more vibration absorption or dissipation is inherently superior to less, but, I have found that that is not necessarily the case.  I heard a CD player placed on various Symposium shelves.  As one moved up the range to the thicker shelves that did more to attenuate vibration, the worse the sound became--even the sales representative from Symposium agreed that this particular CD player was not suited to such treatment.  I have heard the same result with some turntables that become a bit "drier" and more analytical sounding when thin plinths are replaced with multi-layer alternatives that do a better job of attenuation/isolation.

In the realm of vibration control, it really is a matter of experimentation.

 a bit "drier" and more analytical 

Spot on, thanks very much Larry, great explanation and excellent wording. Just wish experimentation wasn't so expensive.