Really good question. One that I am not pretending to know the answer to.
I do feel that the main reason they are successful is large manpower. That is, competent (but not necessarily stellar) leadership can accomplish a ton with dedicated hard workers. This shouldn't be used as evidence that what they are doing is absolutely correct. But, it should be considered when what they do is called into question.
If you have/know of any studies into that, I know I would love to read them. I doubt I am alone.
It is amusing the amount of hubris our industry has. Seriously, you are talking about outsmarting two of the most successful companies out there.
I mean, could they do better? Probably. But it is hard to grok the amount of second guessing any of their decisions get.