Amazon built its own last mile delivery network, and the air freight middle mile in the US (also I wasn't even remotely involved in that), for one simple reason

Amazon built its own last mile delivery network, and the air freight middle mile in the US (also I wasn't even remotely involved in that), for one simple reason: growth. Up until a few years ago, Amazon happily relied on existing carriers. And then Amazon's growth, together with eCommerce growth in general, required massive investment by said carriers. Amazon did some matgs (over simplifying), and came to the conclusion, that for the amount it would have to invest into increased third party carrier capacity it can built in house capacity. And the risk is negligible, since internal networks will handle only so much of the volume. UPS, FedEx, DHL and company are perfrctly able to do last mile deliveries. Some are better in some regions than others. Back the day, Amazon Germany was DHLs biggest global customer. So yes, existon carriers will feel if all their business goes to Amazon logistics. Which it won't, because of risk diversification, and a ton of other reasons.