It got quite a lot, actually, *before* the MGM movie.

Oz is such a weird case; Baum was personally involved in all the early stage and screen adaptations and most of them sound really screwy, bearing little resemblance to the books, though some elements of them got folded back into the later books.

By the time the Judy Garland movie was made, many people considered the franchise long beaten to death. Given everything, it's remarkable that that is even as faithful an adaptation of the first book as it is.