In cases of normal business operation, normal corporate management, delegation, and accountability techniques generally work quite well. Decisions are extensively researched and weighed before being taken. Doing things right, not quickly, is the goal here.
In times of urgent emergency, normal management techniques fail because they can't respond quickly enough. Not because they're inferior, but because they weren't designed for it. Therefore you need one person making big, hard decisions in a timely manner.
There's probably nobody in the world who is better qualified to make big, hard, fast decisions for Amazon than Bezos, obviously. And considering his wealth is tied up in the company too, this is the smart, responsible choice for everyone involved.