In Bob Eubanks' Television Academy interview, he mentions a rumor that Goodson hated Rhyme and Reason so much that its cancellation was one of the caveats for ABC getting Family Feud.
That is plausible, because, as I recall, R&R was somewhat popular for ABC. 
Also from the book:
"Later I found out why our show had been cancelled.  Michael Brockman, who was the head of daytime television for ABC, had always taken care of Mark Goodson, the dean of American game show producers. It was well known in the business that if two shows were competing, and one were [sic] produced by Goodson, his company always got preferential treatment.  Less well known was the fact Goodson hated our show because he thought it was just like the 
Match Game, one of his shows.  Furthermore, what really pissed him off was the fact that Richard Dawson, one of his regular panelists on 
Match Game, had done our pilot.  When 
Rhyme and Reason was picked up and did bigger numbers than the slower paced 
Match Game, Goodson was furious.  About a year later Goodson developed 
Family Feud, which ABC really wanted.  The way I heard the story was that Goodson told Brockman he could have 
Feud only if he axed 
Rhyme.  So he did and Dawson had a new job.  Of course 
Family Feud has become one of the most successful game shows of all time, a staple of network and syndication for most of the last 28 years."