I wanted to keep it very high-level so that a 10 year old could understand so unfortunately some things had to get left out; like Dee. I did link to his book as part of the further reading/resources at the bottom of the writeup though.
One thing if you are interested you should look into is how Visa and MasterCard are basically shunted out of the next generation payment systems in China and India. It actually shows they just can’t keep expanding with economy as competitors either complexly bypass them (WeChat/Pay, Paytm) or the government builds their own (Rupay, UPI by NPCI) which leaves them trailing.
UPI is a system built by National Payments Corporation of India and it is now the most dominant payment system in India in less than just over 3 years since its launch. They support both offline and online payments and increasingly people are not even thinking about credit cards.
I’m still a fan of credit cards and their utilities but increasingly competition is catching up to established behemoths Visa and MasterCard.