Part of the reason I buy on Amazon is the rewards I get with my Amazon VISA Card. I've gotten several nice items for free that way. I can only see this hurting both but perhaps Amazon a little more. Buying from Amazon is more about convenience than anything else. Take that away and I see that hurting Amazon more than Visa. And the majority of folks don't trust crypto-currency, at least at present. Paypal isn't for most older folks as well. They are still a large part of the consumer market.
So Amazon goes with MasterCard. Who wants to go thru the hassle of getting another credit card? Doing so just hurts your credit score.
These two giants will come to a deal. Amazon is bigger but I think Visa has a good deal of leverage as well.
This issue will pass.

$Visa(V)$