I think you're reading too much into this. Specialized stopped selling bikes on Amazon for the same reason Apple (as well as other high profile brands mentioned in the article like Nike, etc.) doesn't use Amazon as the primary retailer of their products - because it's an unnecessary middleman. Specialized is enough of a big, premium brand name that they can drive people to their own online shop directly. Online/DTC sales is inevitable in the bicycle industry, just like it has been for most other consumer products in the past decade, and prior to the pandemic Specialized had made a huge push into online sales to compete with the likes of Canyon (which was a bike company founded to take advantage of exactly this market gap which for whatever reasons the traditional brands were slow to get into).

The online model is also amazing for consumers as well (not to mention small indie bike manufacturers). Instead of choosing between maybe 2-5 bikes that might match my basic preferences and be in stock at my local bike shop, I have dozens if not hundreds of models to choose from made by any manufacturer around the world.

Sure, shops that do bike maintenance are important, but none of what you're saying here explains why any special interventions are needed for them. Won't the demand of more people using bicycles, and needing them fixed, be enough to keep these maintenance businesses healthy? I think bicycle advocates are much better off focusing on getting bikes to more people, and then improving cycling infrastructure to make it safer and more accessible to average people in everyday situations. The number of bike mechanics available is certainly not a major bottleneck that is keeping anybody from taking up cycling today.