How did Lewis create his acids and bases model?
It came from his long interest in how electrons are involved in bonding.
Early in his career, in 1902, Lewis had been interested in the role of the recently-discovered electron in chemical bonding.
In 1913 he proposed that there were two different kinds of bond: a "polar" bond formed by electron transfer, as in Na⁺ Cl⁻, and a "nonpolar" bond that did not involve electron transfer.
In 1916 he proposed that a chemical bond consists of a shared pair of electrons.
In 1923 he redefined an acid as any atom or molecule that could accept an electron pair. A base was an electron pair donor.
His idea of a base was widely accepted. But most chemists still believed in the then-current theory of acids as proton donors.
Chemists did not accept the concept of a Lewis acid until he gave a brilliant paper fifteen years later.