"if the consumer is not lying, then Best Buy advertised a GeForce RTX 5080, but instead gave worthless rocks while taking the consumer's money."

Or alternatively, whoever was responsible for shipping did that, but that's not the customer's problem. The customer only has a contract with Best Buy, so if the GPU did get pinched in transit, then that's between Best Buy and the shipping company.

Charge backs are a super useful lever to pull when all else has failed. They're usually so rapidly resolved that I sometimes find myself wishing I could use them as a first resort and not have to deal with the merchant. Alas, that's not how it works, but it is nice to have a fallback.