History better learned late than never

I've always been interested in history, and the history of science is no exception. I thought I knew a bit about the history of DNA sequencing, so it was a bit of a rude surprise to read the obituaries on Wed for Dr. Ray Wu and discover that he had published one of the first DNA sequencing methods, a method that is credited with being the forerunner of Sanger sequencing. I was totally unaware of this history.
Sadly, the Wikipedia article on DNA sequencing doesn't cover this at all.

A bit of Medline hunting, aided by Dr. Wu's page at Cornell, found a few articles in PubMed, most sans abstracts and few with full text (Somebody PLEASE arrange legally to get classic J Mol Biol as free full text!). Luckily there are a few papers -- this NAR paper and an earlier PNAS one. If I'm reading it correctly, then it involved 2D analysis of digestion maps, which I had heard of so perhaps my historical knowledge isn't totally deficient.

The one question that occurs is why didn't Dr. Wu stay in the DNA sequencing business. I wonder if he left any thoughts -- was it just not interesting enough or did Sanger & Gilbert just jump ahead so he felt like it wasn't the right place to be. Whatever his reasons it can't really be criticized -- Wu had quite a publication record and appeared to be active essentially to the end of his life. It would just be interesting to understand why he took the direction he did.