polito is also a future active imperative of the verb polio
et imperativo modo activâ voce futuro tempore
A mistake it could be, or also a parenthetical ablative absolute: "He [/the man] having been sufficiently polished/educated, ...[the following things happened]"
Mendatum vel ablativum absolutum ut interpositio.
I'm writing in Latin hoping for correction, and not because I'm confident in how I express myself. Latinè scribo ut ab omnibus corrigar, non quod confidenter me exprimam.