Makes a lot of sense really. WWE is flush with peacock money, NJPW business has suffered like everyone's with Covid, there is historic resentment with the AEW situation
If you ignore how shit the TV is- I don't think AEW is much better than Smackdown at the moment anyway*- then there is a lot more potential for fresh matches by aligning with WWE and more money to be made...
*raw feels close to the worst TV of all time at this point