Autistic chap no doubt?
Digits of pi was sort of the Apollo Project of its day. He was a professor of mathematics at one of the first engineering schools in Europe. The complexity of Archimedes method is logarithmic in the number of polygons, 2^62 is only twice as hard as 2^31. I believe had help from his students: He would assign parts of the problem and accept the consensus result as his answer.
Persistent, driven, yes. Autistic, maybe not so much.