the diggings are on way to render the mosque unstable, so that a natural calamity such as an earthquake (natural is up for interpretation here) can simply get it down. So Israelites will try to portray that the mosque fell for natural reasons (and hence avoid taking the blame of causing damage themselves). And then the site is going to be used for Dome of the rock in anticipation for jewish mesiah (aka anti christ etc)
That's the motive as far as israel is concerned.
Not sure about this TABOOT SAKINA ... Israeli plan to build dome of the rock is not even a secret, and the plans architecture etc. is all finalized for it. They are just waiting for certain signs before they get on with it.