WBEZ’s new podcast, “Making Oprah,” traces the 25-year history of the Oprah Winfrey Show. Today, the success of the show feels inevitable. However, when you pull back the curtain you find successes and missteps, reinventions, and moments when it all could have fallen apart. The podcast captures a time when one woman and one show was able to capture about 40 million viewers across the world each week. Chances are that’s not going to happen again.