What is your understanding of why George and Lennie were run out of the last town?

Lennie had met a girl like Curley's wife. George inadvertently went too far in holding or petting her. THe incident would largely have been non-sexual but the encountered spiralled out of control. The woman did not understand Lennie's limitations. The men of the ranch chased them out of Weed. There is, of course, some foreshadowing here.

Oops, I meant Lennie had gone too far with the woman. Sorry.