Nothing has actually changed about the scale of corporations. That's just a popular talking point (it's actually always a popular talking point).
US GDP in 2000: $10 trillion
US GDP in 2018: $20 trillion
Largest market caps in 2000: Microsoft & Cisco, about half a trillion dollars. Double that to match the doubled GDP, and you get an Amazon today.
Amazon is not more powerful than these companies at their peaks: GM, Ford, Walmart, Sears, Standard Oil & Exxon, IBM, US Steel, JP Morgan, AT&T, Kodak, etc
The US Government's spending has more than doubled in size in the last 20 years as well. Its power has dramatically increased as well since the mid 1990s (just the capabilities for control that the espionage improvements and law changes have given them, is extraordinary).