Upper90 pitched me repeatedly raising money for Thrasio. There were multiple rounds of financing, all very large. I could probably find the pitch decks if I dig deep enough. The basic idea was "people can make money as Amazon marketplace vendors. Some people can do this in a smart, automated way, figuring out what things to bulk-import from AliBaba, how much to spend promoting them, etc." Most of the financing was equity-style I think; you put money in now and hoped that at some point down the road they were able to sell Thrasio to somebody else (but to whom?).
Personally I never understood the business; my theory is that if it's profitable enough to be interesting to Upper90's limited partners, Amazon will inevitably squeeze them to capture the margin for themselves. That company doesn't leave a dime on the table.
But that may not be what happened — Thrasio management say the business will continue to operate through and after bankruptcy. If margins had dropped near zero, they wouldn't bother. We'll find out more during the bankruptcy process.