Complex sentence: The Carrs knew Strentzel because he was very active in the Grange movement, and it was Jeanne who first came up with the idea that Louie and John would be a good match, which led to their marriage.
Split into simpler sentences: The Carrs knew Strentzel because he was very active in the Grange movement. Jeanne thought that Louie and John would be a good match, which led to their marriage.