Per the article : "Disney/ABC said the “Brooklyn Nine-Nine” star was unable to continue with the show “due to his successful and demanding film and primetime TV projects.”"
What a crock of crap. If he were that successful, and had moved the dial positively, he would have found time, and they would have found the money.
Terry Crews was awful - ill-prepared, and ill-suited for the role. Chris Harrison is BIG step forward just from the fact that he can handle unscripted television.