Walter left on his own, actually, but he was reading the writing on the wall. He had been demoted from the anchor desk, and his commentaries had been moved from the 10 o'clock news. He knew he wasn't going to last. Honestly, in retrospect, the product wasn't bad, but it was such a departure from their longtime image, it just cemented their 3rd place status. The theme was not great, the graphics were so flashy, and the pacing of the whole show was super fast, for it's time. The overlooked part of this era is the news team, easily one of the best ever assembled at the local level. Lester Holt and Elizabeth Vargas would go on to top dog network anchor status, Jim Avila, Rob Stafford and Larry Mendte would also go national, Jay Levine, Mike Parker, McPherrin, MacLennan and Baskerville are legends, and Bill Kurtis and Harry Volkman are considered some of the best to ever do the job.
Management just sucked.
Here's the newscast attached to that open.
Then consider what the #1 station in town looked like, at that point.
Chicago was very traditional and conservative in terms of news (still is, in many ways), so the WBBM makeover didn't sit well.