Chaim Davis has not left ABMC, he (by way of personal shares and his fund) is a large owner in the company, and as such wants this to be successful just like us.
He has only stepped away from the Director&Chairman of the Board relationship with the company; he is involved in many other business and personal activities and as such as has withdrawn from a semi-active role with ABMC. (I wonder if all those share holders emails might have taken more time then he has available.)