He has said why many times - he is just sick of the circus, and just wants it to end.
Silence does not mean guilt.
Then there is a way to end it and that is in a court of law or in this case a court of arbitration. And he already had attorneys on retainer.
Silence does not mean guilt.
Who are you kidding???
Try being silent in a court case sometime and see how that works for you.
He had the time and money and resources and reasons to contest these charges in arbitration, but chose not to because the evidence against him was incontrovertible.
Nor does it mean, "nah nah, you can't do anything."