The network says, per TV Line, “Glen guided the series creatively for Seasons 2 and 3. [We're] grateful for his hard work. We are both proud of our shared success. Both parties acknowledge that there is a difference of opinion about where the show should go moving forward, and conclude that it is best to part ways. This decision is amicable and Glen will remain on for post-production on Season 3B as showrunner and executive producer.”
So, one more showrunner clashes with AMC. Honestly, what is this "difference of opinion"? Clearly, Mazzara's term on the series is well received with knock-out ratings. I'm curious to know what AMC would rather see or do...