First of all, you have the adoption of the "Pass-Fail" system, which the article notes, when Dean was a student. According to the article, Dean got "seven honors, 17 high passes and 14 passes," which means 7 A's, 17 B's and 14 C's, more like a low "B" average.
Second, most people I know who went to college starting in the late '60's and on through the '70's were the beneficiaries of the phenomenon known as "grade inflation." Simply put, the instructors who were giving guys like GW C's up to the mid-'60's gave B's and even A's starting in the late '60's for work that would have got the student a "C" before.
Dean's transcript gives him nothing to boast about, just like GW's is nothing to be ashamed of.