@BloodyMary
Spoiler!
Because he was not present when she killed. And he had curse so he probably had to maintain distance to ensure her and asiels safety. And he had no interest in that saintess. He brought her probably because she was said to be able to lift the curse.
But I think the saintess is responsible for Blair's death. And ML supposedly was on a rampage after Blair's death until he saw Asiel.