WWE got AEW to burn through a bunch of matches, feuds and debuts. Now, AEW needs to make new stars as they did everything they wanted to do already. It's similar to what happened when the NWO angle ran out of steam in WCW and they had to replace Hulk/Savage/Piper/etc.
WWE also got AEW to take all the people they didn't want anymore. AEW's wasted millions and tons of tv time on people like Cole, Keith Lee, Ruby Soho, Saraya and others who don't draw. These signings also completely changed the company entirely like it did when WCW starting signing up WWF guys. I guarantee you WWE released some of these people knowing AEW would take them.
WWE also took Cody and Punk who were AEW's biggest stars.
AEW won the ratings war and stayed alive, but WWE's winning the marathon.
