1. Because official manufacturers like Goldshell, Bitmain, Microbt etc. have no mention them being the official partners or resellers.
2. Because almost all the hardware they are selling is at a giveaway price compared to what is shown by the official manufacturers. So how do they gain from selling hardware at lower than the official market price? Of course, to lure victims.
3. Because the most of the new hardware they claim to have in stock isn't even in stock in the manufacturer's site.
4. And negative reviews which you have figured out.

They scam each people $10K or 20K+ for each hardware they sell, So yeah, they can afford to hire a good website developer

30% off, on a Bitcoin Miner that has been scarce for months?