The bike business is funny, right? It's one of those businesses where you really need to find your niche in order to succeed. If you think you're gonna survive off a franchise store or something in a strip mall, you will die. Some models that I've seen weather online retail are either going after a captive audience, such as commuters in a city, MTB shops here in Santa Cruz or they cater to super, super high end customers that are paying for an experience (La Biciletta/Blacksmith in Toronto). Lotta shops make up for retail on service as well, but yet again, that requires the captive audience.
In regards to dirt cheap OEM parts from Europe, that's largely stopped. Most of those online retailers won't ship Shimano groupsets to NA anymore and while you can find good deals online, I tend to see them being sold from US-based companies. In any case, with the way manufacturers have shifted away from standards, being your own home mechanic has gotten prohibitively expensive, with the need for various presses and extraction tools, etc... I tend to see many more high-end factory bikes on the road than bespokes and forget doing your own suspension work on modern MTBs...