Certainly education is not a simple problem, but if it is the root cause of incarceration then the simple answer for incarceration is fix education, no?

Yes, but it's not the root cause. it's a factor in criminality, but criminality and incarceration are imperfectly correlated.

Imperfectly correlated is somewhat of a misnomer, IMO. Nearly every observed correlation is "imperfect". Hell, that's basically what "correlation" implies.

Poorly correlated then. Lots of people are incarcerated for things most people consider inappropriate because the criminal justice system is so awash in perverse incentives.

Criminality and lack of education are correlated, but the relationship isn't necessarily causal. It's just as likely they're both influenced by other factors.