So put yourself in Peele's shoes here. You've been pretty successful in your field for several years. You're considering a bit of a career change, a new direction, and you get offered a job. A shit job. One of the only literal shit jobs any performer can ever truly be offered outside of a wacky local plumber commercial. And before you can even decide if you can debase yourself enough to take it, venerable actor of stage and screen Sir Patrick Stewart scoops it up. Sir. He was knighted by the queen in 2010. He took Poop.
So yeah, Peele quit being funny onscreen because that harrowing experience destroyed his desire for it. Meanwhile, Key has also stated that he's done with comedy, because he never really wanted to do it in the first place. The man is a hardcore fan of serious stage acting, and had ambitions to do Shakespeare before fate intervened and made him a comedian. So now he's getting back to his roots, and Key and Peele are apparently truly over.