If you have a giant pile of cash and a bunch of smart people, it may be a good strategy to try to get into as many high volume businesses as you can, shooting for the 1% chance you make a breakthrough on cost reductions in any one of those. You'd suddenly own that industry and mint a fortune in a short period of time. Maybe this is a field bet.
Or maybe Bezos is slightly delusional. I'm not ruling out either possibility.