If I got a First Aid Product Approved by Amazon, after 6 weeks of effort how can another company with no proof of licencing begin selling and piggyback on the listing?

Can someone explain this? I have two Health Canada Approved First Aid products of which I went through quite the devil of a time (frustrating) to get approval (back and forth at least 10 times showing Device ID's, Packaging, Health Canada Medical Numbers, the works) and then finally after 6 weeks listed on Amazon Canada. Both SKU's are now approved and listed at competitive prices and this morning another company out of the blue has piggybacked on the listing. If I did the legal and grunt work and first approvals with Amazon in a comprehensive manner, how does another company with no skin in the game so to speak, no demonstration of Health Canada licencing expertise or anything else freely jump on the listing? FYI - I am not the brand owner but a key buyer of these two items and did all the approval work to list on Amazon.

I'm mystified. It equivalanet to listing a drug on Amazon and getting approved. Then along comes another seller who then sells the same item on my listing? Does not the new seller also have to show where they get the item and also get approval for the same listing on Amazon.

This is different from owning the brand. I do not own the brand but merely went through the detailed work to get the item listed.

I understand piggybacking. Its the reality of selling however if its a medical item such as a first aid say special O2 fitting, does not another seller also have to go through a similar Health Canada (also think FDA) proof process to list on Amazon?