[BurningFrog]

"Winner-take-all" is an end result, not an explanation.

The explanation, or part of it, is a unified interconnected world market where even a tiny idea, well executed, can be incredibly well rewarded, since it scales across the economy of most of humanity.

Nobody really "constructed" it. It emerged.

[TimJYoung]

Of course it was constructed. Aliens didn't just drop it from the heavens - the US specifically released the internet to the public and commercial interests, whereas previously it was limited to academic interests. Once commerce was up and running on the internet, it was simply a matter of companies getting big quickly and inserting themselves as middlemen between customers and producers/distributors. The fact that most of these companies eschewed profits for many, many years in favor of growth makes it self-evident that they understood that capturing the majority of the network (winner-take-all) was the primary goal.