The irony is Lew hatched All News 106.7 at a time Cumulus was losing millions during the Rush Limbaugh advertiser boycott. Talk was toxic. He signed Fox5 as a content partner and lured out-of-work CNN Radio alums for $20/hour. It may have been a fool's errand to challenge WSB, but it wasn't a suicide mission. Kimmer was restless on his Massachusetts horse farm and wanted back on the air. By that time, Lew was out of the picture.
I assume that a company as big as Cumulus has some newstalkers that carry Rush, but I don't think a Rush boycott (which happens every couple years, so nothing new) was that big of an impact on Cumulus's finances. Cumulus's problem was debt and leverage, same problem as iHeartClearChannel.
It was 40 years ago, but WGST did very well with an all-news format in the late 1970s and early 1980s. Of course, WSB finally woke up and entered that space, dumping the Morning Merry Go Round and getting serious with radio news (having a clear channel signal that works when the sun isn't shining during AM and PM drive also helps). WGST added talk by the end of the 80s, being one of the first Rush affiliates. Cox co-owned AJC ran columns about their competitor's "hate talk", until the folks at White Columns started poaching all of WGST's shows and talent (Clark Howard, Neal Boortz, Sean Hannity, and finally Rush).
WSB-AM has been a follower, but a fast follower and they go all in and dominate when they do.
Heck, when Cox was LMAing WCNN for a time in the late 1990s, they had an all-news format on that station. Heck, that's how and why talk WRNG Ring Radio flipped to WCNN, which got started airing the audio of CNN Headline News (hence the callsign) in the early 1980s.
Meredith tried it on WGST in the 1970s and early 1980s after they bought the station off of Georgia Tech and had a nice run. Ring Radio tried it on WCNN in the mid-1980s and had a nice run. Cox tried it again on WCNN in the late 1990s. So, definitely not a suicide mission and a plausible format hole in the market. IMO it failed because people don't get their news from radio as much anymore, particularly national news. It's not the 1990s anymore.