Lyle really wasn't that good. His reputation is based mostly on fights he lost, to Foreman and Ali. His upset losses to Quarry, Young, and Lynn badly exposed his limitations.
On further thought I am downgrading my estimation of Mr. Lyle. His name today would be Clifford Etiene (minus the 2nd prison sentence). He wasn't all that powerful and he wasn't all that good but he did go to prison. Mostly basked in the artificial glow of an overrated era.
Quarry was past his own prime when he fought Lyle, and Lyle was the heavy favorite to beat both him and Young. Lyle was lucky to have even got a title shot.
True, although i don't really think it's that bad he quit. He was hopelessly behind and didn't land a single meaningful punch in the entire fight.