I recently worked on a fraud detection POC with a few vendors in this space and it is common for them to require adding a js snippet to capture info like this. This isn't out of the ordinary behavior.
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Whether or not the money is actually safe or not doesn't really matter when the card networks routinely assess penalties that affect the business. Running cards that have transactions that are later disputed, or for having too many disputed transactions in a certain period of time gets you penalized. The card networks do not make consumer protection programs free, and so fraud prevention happens at every layer. It is as much a battle between a vendor and the card network as it is a battle between a vendor and fraudsters.
Unless you are Alex Jones, it is probably not worth it to redesign your website to accommodate doomsday preppers. I just disabled JS and you can't even sign in to Amazon or eBay without it. Most websites are now heavily built on JS frameworks, so most projects I have worked on would not be meaningfully functional without it.
> Aren't those credit cards safe because they are electronic and todays transactions can be reversed, tracked and that fiat money are just database rows?!
No... The reversal doesn't prevent someone from buying something and taking the item. Sure you can reverse the transaction, but then the merchant takes the hit.
Credit cards are safe for the consumer because transactions can be reversed and tracked. They are not safe for the merchant.
In your example, allowing Amazon's JS allows the site to work at least as far as AWS Console behaves. I don't really use eBay, so I can't speak to what JS is required.