According to that person, on the same night Su Wan approached him, someone else reached out to him, but not in person, it was through a phone call, promising him that as long as he followed the instructions, after the job was done, the person would pay him double.
People like them live dangerously, with their lives on the line. As long as they get paid, they'll do anything, except take a life.
As long as no one dies, even if caught, it's just a few years in prison, and he doesn't mind.
So when Su Wan approached him, he didn't refuse. But when he learned that Su Wan wanted someone's life, he refused, only to receive another call that night.
According to that person's words, he just needed to follow Su Wan's instructions, and they would ensure Sheng Jiayu was rescued, so he wouldn't have a death on his hands.
Whatever entanglements they had didn't concern him; he just wanted the money, so he agreed without hesitation. Of course, he'd say yes to such a great offer.
