Does anyone know why the original "Becky" left Roseanne?

Yup, college. Alicia "Lecy" Goranson wanted to attend college in real life. I think she went to Var. They replaced her with future "Scrubs" leading lady Sarah Chalke. Goranson came back to the show briefly during season 8 and I do recall there is a episode where Darlene asked Becky a particular question, "Where the heck have you been?," and I believe it refers to Goranson as the old Becky when she returned.