A lot of "genuine" snake oil is sold and shipped by Amazon, too.
That could be due to the constraints related to your location.
Sometimes, when I read shipping terms, I feel for you guys in AK, HI, PR, etc. If they'll ship there at all.
Even in a major metropolitan area, with Amazon trucks traversing the streets every day, it will still task the USPS with the final mile delivery, which for me usually happens with the small stuff.
Judging by the stuff I order from overseas, I've found that logistics can often seem to be the opposite of what the term implies, especially for low-cost shipping methods.
At the least, a package will have two labels on it, from the original transit courier, to the final-mile courier. But the most I've ever seen had four or five, and passed through many hands around the globe to reach me.
In the modern world, it's much easier to set up a business that doesn't require the hard capital investments needed in the past, have it become very successful, with customers who have little to no idea as to how it operates.
Again, the Parts-House-BITOG-Loves-to-Hate-But-Can't-Stop-Patronizing, RockAuto, is probably the best, and still peristent example. Without a WorldPac, SSF, or other wholesalers who drop ship, a lot of online parts retailers wouldn't exist.
But more than once, when I've shopped for things, and see something interesting from an unfamiliar brand with a very nice, professional, and polished website…have found that in truth, the business operates from a mailbox rental storefront in a strip mall, when they dare to list a physical address in their contact information. Many don't.
Not saying that is, or isn't necessarly a sign of legitimacy, but if it's a costly item, or isn't commensurate with the image presented, the Spidey Senses do kick in.