Zappos is an Amazon subsidiary even if it does operate quasi-independently (and quirkily from a management perspective). It looks a lot more like Amazon though with generally far less emphasis on building out infrastructure. Ultimately it's sort of a niche because of the nature of selling shoes online.

Zappos is now an Amazon subsidiary. It grew sustainably for a decade before Amazon acquired it.

Yes. In many ways they grew more in the vein of many traditional mail order catalogs than Amazon.