Really. He had only been a county executive and Deputy Secretary of the Navy. Deputy Secretary of the Navy!!
State Senator, not County Executive. Also, during his time in office, he de facto led Navy Department.
1. His name
2. He was very energetic campaigner
3. He was well-conected
VP candidates selection process was diffrent in those years. Tahe John Kern for example in 1908: he was just a state Senator. Or take Garret Hobart in 1896: another State Senator. Chester Arthur? Did not held an office before. Arthur Sewall? Same.
But all were prominent members of the machine/establishment.