Adding to the mystery, I read the newyorker article (2009) linked from wikipedia on Eurisko, and it seems Lenat forgot the winning strategy Eurisko developed, or the first article is wrong.

"Eurisko, however, had judged that defense was more important than offense, that many cheap, invulnerable ships would outlast fleets consisting of a few high-priced, sophisticated vessels. There were ninety-six ships in Eurisko’s fleet, most of which were slow and clumsy because of their heavy armor" - 1984 article

"astronomical number of small ships like P.T. boats, with powerful weapons but absolutely no defense and no mobility, Lenat said. They just sat there. Basically, if they were hit once they would sink." - 2009 article