This is turning into circular logic. IF Brian was actually able to influence the situation, why did all the bad things that he so anxiously points to happen? If he had no/little influence, resigning was absolutely the right thing to do - send the message, and put an end to his pawn-like role.
And the suggestion that Brian was "chased off" by anyone is a discredit to Brian - worse than anything I said. If he's that weak in fortitude......
JMHOs,
SGE