what was the only thing that kept tom from leaving the organization he joined

The only reason that Tom joins the Cadets of Temperance is to wear one of their showy uniforms. Membership becomes too much for Tom because he had to swear off everything that he finds integral to his being (smoking, tobacco chewing, and cursing). Tom resolves to wait until old Judge Frazier dies thus facilitating wearing his fancy costume in his funeral. The judge gets better and Tom quits the club. The next night the judge relapses and dies. You have got to love the irony!