"This has not prepared him well."

Note: "lo" corresponds to accusative, and "le" to dative of "él".

Why "no lo" instead of "lo no"?

Argh! I forgot that you can attach the object pronoun to the present participle (gerund) but not to the past participle.

Why not: esto no le ha preparado a el bien

Question: Why is "lo" required in the answer of "Esto no lo ha preparado bien a el."