Scammers Thrive on Amazon-Amazon won't do a Thing to Stop Them

Has this happened to anyone else? A customer bought an order on December 13th and it delivered to the individual on December 16th. The order was signed for by the purchaser and I have the proof of delivery. We closed for the New Years brake on Friday December 29th. The customer then contacts us through Amazon saying that he didn't receive his product that Friday after business hours and he wants a refund. He claimed to Amazon we wouldn't respond, but we just were not in the office and it seems he knew that we wouldn't be. Amazon refunded him without ever looking at the tracking showing that it delivered. Then, they denied our claim when I fought the scammer for our money back proving that it delivered to him on time. How can Amazon do that? How can such a tech savvy company not understand how to track a package? How can they protect scammers more than the sellers on their platform? Scammers Thrive on Amazon-Amazon won't do a Thing to Stop Them!