Capital One has built their first airport lounge in DFW; it makes sense to advertise their credit cards. The ad spaces are controlled by the airport, not AA, although airlines have historically been able to complain about certain ads (Emirates used to have a large ad in LHR T5 until BA complained enough IIRC).

Generally the airline co-brands have better ways to advertise in-airport (since they get access to airline-controlled ad spaces and the airline is invested in pushing the cards since they get a cut) than general advertising -- paying for a lot of eyeballs not flying the co-brand airline being advertised is a poor use of money. Amex and Capital One have credit cards that give lounge access no matter which airline you are flying, so it makes more sense for them to purchase general advertising like in your picture.

Incidentally, Citi is not allowed to advertise their AAdvantage cards in airports at all -- AA has both Barclays and Citi as issuers and Barclays has exclusivity on airport advertising, though they are not allowed to within 100 ft of an Admirals Club.