Amazon's a platform company. Their future counts on continuing to build new platforms, continuing to grow old ones, and continuing to find synergies between them. Starting with their e-commerce platform, they've identified each component of their businesses that they can cut costs by doing themselves, and bring in new revenue by offering its at-scale operating efficiency as a platform of its own.
They started with shipping and logistics, then web services, now media & entertainment distribution. It's rumored they're rolling out smartphones of their own soon, and I suspect it's more to extend the reach of their content distribution platforms than because they really want to achieve dominance in the consumer electronics market.