Kane left in a big hurry when one of the men asked him to think about Amy. Kane did listen and took off out of town. I think the only reason why is because of the safety of his new wife.
Kane was out of town and on his way to a new town and he decided all of the sudden that no matter where he went that Miller was bound to find him. I think that Miller probably wouldn't have followed him but Kane was afraid that if Miller did follow him that he would probably catch up somewhere in the open desert and he wouldn't have any help. And Amy Is a Quaker and is opposed to violence and what not. Kane's wife even tries talking him into leaving with out knowing anything that is happening and he doesn't even listen to his own wife who he married not even ten minutes before. Kane rushes back to town like the idiot he is and his wife tries one last attempt to stop him from meeting Miller by threatening to leave on the train, he doesn't care and she leaves for the train station. Kane looks all over town in search of a posse but only one man and one boy wants to help, everyone else in town isn't an idiot and doesn't want to die. The whole town tries to talk him into leaving but Kane has more pride than that and refuses to leave. As a town they appreciated all the hard work that Kane did for them. Kane also put Miller in jail for the town and now he's coming back and no one can even lift a finger to help this marshal, that cleaned up their town and turned it around, defend himself against Miller and his posse. .
More over, the entire town thinks that if Kane isn't there everything would be alright. I don't think so. Miller and his posse are feared by everyone, so wouldn't that make him want to cause some trouble when he comes back weather or not Kane is there? The answer to that is yes, you ask why? Because Miller went to jail for 3 years and he"ll be wanting to commit some criminal acts.