Also, he didn't choose Happy Endings. Actors who sign on for show pilots are released if the show doesn't get picked up, but otherwise they're contractually committed for five-plus years. He had a fallback plan since at the time he shot the New Girl pilot it looked like ABC was going to bury Happy Endings and there was no chance of renewal, but once HE was renewed, he had no choice.
That said, I like Wayans Jr on Happy Endings AND I like Lamorne Morris on New Girl. Morris has a pretty low-key vibe, but that's fine.