what causes bigger to, stand and see vague relations that he had never dreamed of?

"He wondered if it were possible that after all everybody in the world felt alike? Did those who hated him have in them the same thing Max had seen in him, the thing that had made Max ask him those questions? And what motive could Max have in helping? Why would Max risk that white tide of hate to help him? For the first time in his life he had gained a pinnacle of feeling upon which he could stand and see vague relations that he had never dreamed of. If that white looming mountain of hate were not a mountain at all, but people, people like himself, and like Jan—then he was faced with a high hope the like of which he had never thought could be, and a despair the full depths of which he knew he could not stand to feel. A strong counter-emotion waxed in him, urging him, warning him to leave this newly-seen and newly-felt thing alone, that it would lead him to but another blind alley, to deeper hate and shame."

Max had just come in to offer Bigger his services as a defense lawyer. He wasn't there for the money, because Bigger had nothing to pay him, and he wasn't there because he believed Bigger to be innocent. He was there because it was the right thing to do.