Arbitration does not and cannot cover crimes. Arbitration is a civil matter. I would imagine that the arbitration agreement included a clause along the lines

Arbitration does not and cannot cover crimes. Arbitration is a civil matter. I would imagine that the arbitration agreement included a clause along the lines of "Alphabet will not pursue any further legal claims against Levandowski related to his time of employment." and vice versa. I could be wrong, of course, but I doubt arbitration left open a lot of space for future action. Without the arbitration being unsealed, though, I have no way of knowing. Of course, the US DoJ and/or California equivalents can still pursue criminal charges against Levandowski.