Right, as the sole judge in deciding whether to uphold the suspension, Goodell was in a very powerful position. I would say too powerful, however, this was a part of the CBA and both sides agreed to this set-up. In that position, Goodell was faced with either upholding the suspension, reducing the suspension, or completely overruling the suspension. He chose to uphold the suspension, and I think the main factor in his decision was Brady destroying his phone.
In light of Brady destroying his phone, Goodell would have looked suspicious in the eyes of many other NFL players had he even reduced the suspension. That's why I think Goodell decided to uphold the suspension and let a Federal Court decide the issue. The question becomes, was Goodell also prepared all along to appeal in Federal Court. And then if so, does the NFL have a good case for appeal. That is where I am uncertain because I haven't followed this, but I do know that arbitration agreements, just like the agreement in the CBA, tend to be considered valid contracts by most Courts.