I ran a 2:27 marathon while a full time partner in a 20 person law firm and have competed at the sub-elite level during my 40 years as an attorney. I ran 70-80 miles per week until age 60. As several have mentioned, you need to get creative to get in the mileage. I commuted 2-3 days per week on foot, running 4 miles to work and a roundabout route going home of 7-10 miles. (We had a shower and locker room in the office.) I also did the commute on foot thing to kids' soccer and basketball games. It helped that my wife is a physician who also worked hard so she did not mind the time I spent running. It also meant that we had the resources to hire nannies, house cleaners and gardeners to free up time.
Someone mentioned George Riley as an attorney runner. I competed successfully against George in running. I was not at his level in the legal profession. My practice primarily involved commercial real estate (both transactional and litigation).