#3. Best way to transition the belt to a babyface
The entire idea of a "transitional heel reign" has been a concept for decades. It's like how Ivan Koloff won the WWE Championship from Bruno Sammartino so that Pedro Morales could become the new babyface champion.
Similarly, The Iron Sheik defeated Bob Backlund for the WWE title so that Hulk Hogan could become the next babyface champion. It's a simple and effective way of getting another superstar over while not affecting their popularity by defeating a babyface champion.
In this case, Charlotte Flair won her ninth title, but once again, it was just a transitional reign and Bayley ended up being the beneficiary. It's crazy to think that so many of Charlotte's reigns have been transitional in nature.
Either way, it's an easy way of getting her to 16 championships. And it worked in this case because Bayley got a whole lot of momentum back.