I find it weird how fraud protection is used to justify why these companies are so popular because fraud is not something that most consumers care about up front, most people only start caring when it happens to them. Most tend to assume that every tool they use is secure by default. "This product is not insecure" is not a very compelling selling point IMO.

It's actually difficult to justify Stripe's popularity aside from media monopolization preventing alternatives from gaining mindshare. Everyone knows Stripe but many don't know about the existence of alternatives.