Higgins was literally drinking a beer in his car at the time he ran the Gaudreau brothers over, and he had "five or six beers, but not in two hours". He admitted it to police, in his own words. He tested over the New Jersey legal limit with 0.87.
More than that, however, was the fact that Higgins drove like an absolute road raging maniac, swerving into their lane and running them over. The Gaudreau brothers being intoxicated didn't matter because they were apparently following cycling laws, not swerving in front of cars, etc.
They would not have been killed if Higgins wasn't swerving into their lane like a maniac, and he has a history of road rage.
I don't blame the defense attorney for trying every avenue; that's what you're supposed to do as a defense attorney, to give your client every avenue, so that if they are guilty, there's no doubt about it. Checks and balances and all that.
But Higgins is far from a sympathetic figure. I feel for his family, I especially feel for the Gaudreaus, but as someone who has lost a close friend to a drunk driver, I have less than zero sympathy for Higgins himself. I just want the defense to try everything reasonable, so that if he is found guilty, he spends a good portion of his life in prison.