None of these companies had to deal with the current investment environment. It's an arms race. While it's a chicken and the egg issue since both Facebook and Google provide virality and discovery, respectively, and it is those two features, virality and discovery that lead to a positive return on investment from blitzscaling.

Besides discovery and virality, there is also the issue of falling transaction costs. When Google, Facebook and Amazon were founded, you had to maintain your own datacenters and infrastructure. That alone produced a massive barrier to entry that made competition less fierce. Since the advent of AWS and other cloud computing platforms, transactions costs for tech companies have dropped dramatically so you can't rely on infrastructure prowess as a competitive advantage for many tech verticals.

You simply can't compare companies that were born and matured in different markets with different dynamics to those founded in the past 10-15 years. It's apples and oranges.