I remember when Paypal received bitcoin last October (iirc), and it didn't have much effect on the bitcoin price even if we know Paypal has more functions than Amazon.
Same news have different effects if they are released at different times of the general market and of one coin. Bitcoin and Ethereum was lifted up too high and they need correction. Even good news like that, can not help them rise up more immediately.
If you recall to what effects the Libra news brought to bitcoin, it is the right time to pump crypto market after months of bearish. A vague news from Libra heated the market and moved it up.
I don't think the ETH case will make any difference. What I understand from this news, Amazon only makes use of the ETH blockchain in its platform. I don't know technically whether this will impact the traffic congestion of eth mainnet later on.
The market now is heated a lot and top 2 coins as Bitcoin and Ethereum will have a long correction. Capital will not stay in them for long and other smaller altcoins will move up.