according to Wright, who's to blame for biggers crimes? why?

It is difficult to lay blame on one person. Certainly Bigger bears responsibility for his own actions. Beyond that certainly it was not easy being black in 1930's America. They were made to feel an underclass. To young black men like Bigger, there was little opportunity to transcend their status. There were few role models and white society prevented few positive avenues to break the cycle of poverty and anger. The problem is much too complicated for this forum but certainly Bigger was representative of many young Black men at the time and perhaps even today.