This is utter speculation but I have a feeling there was some behind the scenes drama going on
George Corleone finds out about LMH's original (unauthorized?)appearance on Knapp's weekend show gets pissed and cancels it. A big brouhaha ensues, cue ultimatums, "I'm too old for this shit" etc
LMH basically retires from radio interviews, claiming they take too much prep time(but then does 2 shows in 48h)
LMH unceremoniously dumped from C2C with no big farewell show with George but is allowed a final half segment on Knapp's weekend show