Definitely "après lui" - disjunctive pronoun here rather than direct object pronoun, weirdly enough. Those are the moi-toi-lui-elle pronouns instead of je-tu-il-elle or me-te-le-la, etc.
"Après il" would be like saying "after he," if that makes sense!
no subject
"Après il" would be like saying "after he," if that makes sense!