This was not meant to be a mini-series, but a series.
The original RMPM was groundbreaking television and the reason why so many restaurants are closed on Mondays even today. Monday nights were "Rich Man Poor Man night", and people stayed home to watch the mini-series since very few people had VCRs back then, and recording shows was not a common option.
After the mini-series, the producers saw an opportunity for a steady stream of cash from an open-ended series. They offered Peter Strauss more money than he thought he would ever be able to make in his life, which he of course accepted. They made the same offer to Susie Blakely, but she declined because she believed she was destined for movie stardom. She did accept to appear in the two-hour pilot on the condition that her character be killed off in the first hour!
The ratings of Book II were consistently good but not great. Production costs were very high since they had hired the very best writing talent and had them working around the clock. By the middle of the first season, it was becoming obvious that the ratings were simply not strong enough to justify the costs. The audience missed Julie Prescott / Susie Blakely and just couldn't get used to Maggie Porter / Susan Sullivan. Bringing back Kay Lenz as Kate Jordache and making her part of a love traingle with Rudy didn't lift the ratings. So they wrapped up the story toward the end of the season 1 and repackaged the whole thing as a second mini-series.
The legacy of Book II, though, was that it became a template for prime time soap operas. Dallas premiered a year later, and they were off to the races.
Interestingly, there was a plan for a Book III with major production redesign. This one would be more of a police drama vs. Soap opera. Rudy will have survived the gunfight with Falconetti, but he leaves the senate to become the Director of the CIA. The show was supposed to be about him leading an agency to battle terrorism. All networks hated the concept and refused to pick it up. But the creators hung on to the idea and made it into a TV movie called Under Siege a decade later. Peter Strauss returns but legally they were not allowed to make any references to RMPM since ABC owned the rights and the TV movie was produced by NBC. That said, the character that Strauss plays is clearly Rudy Jordache, by another name. That TV movie was meant as a pilot for a new show which was never made.
