And Amazon is selling returned items as new without inspecting them. Causing customers to get scammed in turn when Amazon is with fake returns.

What's ebay supposed to proactively do here when every product they list is not in their possession? Car parts don't exactly come with certificates of authenticity. At best, it's a box that's either been reused or reprinted by the counterfeiter. They do offer an escrow service for things like sports memorabilia, things that have authentication experts. The most they could really do is ban sellers with repeated reports of selling counterfeits.