Sounds like strictly a financial move. From Tom Taylor's NOW Column...
Bob Sirott and Marianne Murciano will host their last noon-3pm shift on Tribune’s talk WGN tomorrow. No mystery about why. VP/Content and Programming Todd Manley tells the Chicago Tribune “Right now, we need to invest in one less show…it’s just a matter of resources.” WGN will cover the schedule by spreading out existing talent, in the lineup that was revamped by GM Jimmy de Castro starting in 2013. Husband-and-wife Bob Sirott and Marianne Murciano have both done radio and TV in the Windy City, and Bob says “It’s been fun to be able to do whatever we wanted” on WGN. New lineup starting Monday is Steve Cochran, 5am-10am. Bill Leff & Wendy Snyder, 10am-noon. The Wintrust Business lunch with Steve Bertrand. Then Bill and Wendy, back for 1-3pm. Roe Conn, 3-7pm. The Download with Justin Kaufmann, 7-11pm. Patti Vasquez, 11pm-2am. And Nick Digilio, 2-5am. What’s next for Bob and Marianne? Bob says “After Friday, we’ll be going out to dinner, I guess.”
It was clearly not a contentious parting of the ways or they wouldn't have allowed these last two shows.