That doesn't make any sense. Visa & MasterCard are the intermediaries, not the actual source of the cash. They sell their merchant network, and recreating it would be hard (not impossible, but a lot of work not in Amazon's wheelhouse).
Chase or Citi or Wells Fargo or whoever is the bank that needs reserves and fronts the cash to the merchant, and earns on the interest rate and fees and takes the risk on defaults.
Chase or Citi or Wells Fargo or whoever is the bank that needs reserves and fronts the cash to the merchant, and earns on the interest rate and fees and takes the risk on defaults.