Al Jean (https://en.wikipedia.org/wiki/Al_Jean) for those who don't know, has been the show runner since Season 13 (https://en.wikipedia.org/wiki/The_Simpsons_(season_13)). It seems like for better or worse, one of the first things Jean did when he took over was undo practically every character change (unless it was regarding a Simpson such as Lisa's vegetarianism) that happened during the previous three showrunner tenures (David Mirkin (https://en.wikipedia.org/wiki/David_Mirkin), Bill Oakley (https://en.wikipedia.org/wiki/Bill_Oakley) & Josh Weinstein (https://en.wikipedia.org/wiki/Josh_Weinstein), and Mike Scully (https://en.wikipedia.org/wiki/Mike_Scully)) since now that The Simpsons was essentially his show and their position on the Fox hierarchy was secured. On that end, Milhouse's parents got back together, Barney fell off the wagon, and to combat Maude's death, the show would just figure out as many ways as possible to incorporate Maude via flashbacks or the afterlife. In essence, it seems that Jean wanted things to revert back to a "daily strip" format of wackiness in which secondary and tertiary characters would be put back into their place and the show could once again focus exclusively on the Simpsons.