It was the political science department, not the philosophy department. (For academic purposes, political philosophy is a subfield of political science, not of philosophy.)
I'm not sure where your curiosity comes from—Crawford is presented in the story as taking a break from his academic career to work on the motorcycle. There's no continuity between the two things except his own personality and involvement.
I absolutely cannot stand that book. It's largely a narcissist making superficial observations about what "doing a good job" means in the face of his son's very real mental health struggles.
To each his own. I took it as him admitting his failure at "doing a good job," and his son's mental health struggles as just being a kid. Riding a motorcycle, camping in a tent, and hiking in the mountains are exhausting. I'm 29, in reasonably good health, and after a week of hiking even I am glad to take a shower and sleep in a proper bed.
I'm not sure where your curiosity comes from—Crawford is presented in the story as taking a break from his academic career to work on the motorcycle. There's no continuity between the two things except his own personality and involvement.