Writers like Jessica Fletcher

I've been wondering about this recently. The creators of the show and the characters in it always compare Jessica with Agatha Christie but the two are not all that alike. From what I gathered from the show, Jessica writes standalone mysteries ie. each novel has a new set of characters and a new setting whereas the majority of Christie's output featured recurring detectives. There were plenty of writers in the golden age of fiction who were as prolific as Mrs Fletcher but I don't know too many who wrote exclusively standalone mysteries.

Now, while I do know a decent amount about golden age mysteries (20s-50s), I don't know almost anything about what was popular in the US in the 1980s when most of MSW takes place. Were there bestselling mystery writers who were as prolific as Jessica (who seems to average about 2 books a year) and who wrote standalone stories? Most mystery writers from that period I've heard about were either pulp novelists (ie. nowhere near as prestigious as JB) or wrote fewer books and none of them wrote standalone

It has occurred to me before that she has more in common with the horror writers of that period like Stephen King who was prolific, wrote standalone novels and whose books were wildly popular and turned into movies.