The demo breakdowns say otherwise. The nxt audience is much older than the aew audience. They aren't appealing to the same audience except when there is something heavily hyped that will usually draw from each others audience.
the bolded tells it all. AEW viewers obviously have eyes on NXT's product if they know beforehand that an NXT show is supposed to be good. thats when the ratings are closer - or NXT might even pull out a win. if NXT didnt appeal to the AEW audience, this wouldnt happen. AEW fans watch both shows. difference is, NXT just isnt as good, plus its more accessible. you could easily just watch it the next day. thats exactly what most people do. they watch AEW live, then check out NXT the next day. the demo numbers(which arent even based on accurracy) dont tell you all that.
they pull talent directly from the same pools. the champions from both shows are from the same stable for pete's sake. NXT was geared towards AEW viewers, long before AEW even existed. thats why i always say, AEW would be doing over a mil easily if they went up against raw or smackdown.