Amazon becomes their best available option, and once they work there for a year or two, improve their skills, get some experience, and get tired of dealing with hell that is working at Amazon, they get hired at all those companies they couldn't initially get into. No one says Amazon is incompetent at tech, quite the opposite. There is a lot people can learn while working there, and all those other competing tech giants know it.
I've heard of very few moves the other way around, and in every single such scenario I personally witnessed, there was a lot of very specific circumstances for the person that lead them to that point.