Amazon originally built out server capacity to handle the huge order surge for the Christmas holidays, and found that they had spare server capacity the rest of the year – and a huge capability in managing servers. So they expanded into the adjacent space of cloud computing (Amazon Web Services).
They’ve also built out a delivery and logistics shipping capacity to handle their own surges, and that gave them tons of extra capacity. Amazon delivers more of its own packages than other shipping services combined. They delivered over 3.5 billion packages last year, making their own internal shipping business two-thirds the size of UPS.