I think the deal makes some sense for both teams.
Obviously, Mbah a Moute is not a core piece of the Kings going forward, and getting a chance to rehabilitate the (barely started) career of a former #2 pick is a low-risk move. However, the Kings are going to have to devote the necessary resources to develop Williams. Part of that will mean giving him minutes, perhaps even if he hasn't earned them, and the Kings are crowded in the frontcourt. They also need help at SF now, having traded probably their best option there. So a follow-up move is badly needed for roster balance.
Wolves fill a position of need with a smart and gutty defender. Mbah a Moute can play either forward spot for them as needed, giving them some good depth. It won't elevate them above the rest of the West, but it's a good move towards strengthening the roster.