He was only on the air for “political reasons.”
bttt
CBS didn't start the show for political reasons, they started the show because NBC chose to go with Jay Leno after Johnny Carson retired, so CBS wooed David Letterman to counter-program a late-night show against the network that passed him over.
They even offered to refurbish the Ed Sullivan Theater to sweeten the deal.
Letterman was actually very funny, UNTIL he became political in his later years (and after allegations of sexual harassment and a hostile work environment at his show). When Letterman retired and producers chose Stephen Colbert (from Comedy Central's The Daily Show) to take over, the show became all politics all of the time.
I think CBS just got tired of the sinkhole in their schedule, and will go back to running repeats of its prime time schedule in the late-night slot. Maybe Trump can make CBS an offer for the Ed Sullivan Theater, too!
-PJ