Why did Mendele Mokher Sefarim first turn from Hebrew to Yiddish for his novels?

Mendele Mokher Sefarim (the pseudonym of Shalom Jacob Abramowitsch) turned from Hebrew to Yiddish for his novels primarily because he found the contemporary Hebrew literary style of his time to be "wooden" and overly imitative of the Bible.1

He became convinced that biblical Hebrew was unsuitable for depicting modern subjects and contemporary life. By adopting Yiddish, he was able to capture a sense of "homeliness" and express the lively humor and biting social satire he desired for his stories.21

Mendele eventually returned to writing in Hebrew in 1886. By incorporating Hebrew and Aramaic phrases from the Talmud, he successfully developed a new, flexible style that allowed him to maintain the expressive qualities he had previously achieved in Yiddish while writing in Hebrew.12