It's a combination of factors. As mentioned in the original link, PayPal has an advantage because a portion of transactions are done internally using PayPal bal

It's a combination of factors. As mentioned in the original link, PayPal has an advantage because a portion of transactions are done internally using PayPal balance. This results in an instant and free transaction. They also have a network effect which is compounded by saving the buyers'payment information, meaning the buyer doesn't need to resubmit their payment information on each transaction. The company treats its merchants terribly and treats buyers like royalty. This is a winning strategy because merchants have no choice but to use the payment methods the buyer prefers. Otherwise the buyer will simply go to a competitor who does take PayPal. PayPal is an essential service to most merchants. The way they close and limit accounts can basically determine which businesses in a specific industry are successful. They seem to selectively enforce their own policies among merchants. This will create monopolies or oligopolies simply through having a functional PayPal account. Considering this huge power they hold, it is unfortunate that their policies are so opaque and inconsistent. A merchant is in a constant state of fear that one day PayPal will just permanently close their account, and will have no option to discuss or appeal the decision. It happens constantly and is the reason many businesses eventually fold.