Credit card chargebacks are controversial obviously, but I always assumed that the card issuer did some due diligence and gave the vendor some opportunity to give their side of the story.
What's interesting about this case with Ryanair, is how they wait until the passenger is about to board the aircraft (through a subsequent booking) <correction at check-in time not boarding> and then ambush them with the demand to repay the chargeback. At that point you are under duress and stand to lose a lot of money if you can't travel, as opposed to when you are just booking the flight and might simply choose another airline.
It doesn't feel right that that kind of behaviour would be legal. Companies and individuals will regularly do business with each other while they might be in dispute over something else. That's why we have the courts for example. What if other companies did similar things after they felt their T&Cs had been broken in some way? There was such a case in Germany where Lufthansa sued a passenger, but they lost the case, and didn't get to unilaterally impose their will like Ryanair is here.
https://www.irishtimes.com/life-and-style/travel/ryanair-bars-passengers-from-flying-unless-they-repay-pandemic-chargebacks-1.4698690