That ['DARPA created the Internet'] wasn't the point they made though.
If anything I think your "many other networks" example reinforces the point. The private sector left to its own devices came up with tons of incompatible small networks all vying to be the juggernaut.
The government, when faced with much larger problems than growing market share, instead invested considerable resources into solving a problem in a way that could handle the needs of a large national government, and then later invested more resources into making that internet a public good.
Even if the government hadn't developed its own internet protocols (and standardized on a notional private sector one), the government would likely still have been instrumental in expanding the use of some other standard. E.g. Eisenhower didn't invent the road, but his Administration sure did ensure a lot of them got built.
If anything I think your "many other networks" example reinforces the point. The private sector left to its own devices came up with tons of incompatible small networks all vying to be the juggernaut.
The government, when faced with much larger problems than growing market share, instead invested considerable resources into solving a problem in a way that could handle the needs of a large national government, and then later invested more resources into making that internet a public good.
Even if the government hadn't developed its own internet protocols (and standardized on a notional private sector one), the government would likely still have been instrumental in expanding the use of some other standard. E.g. Eisenhower didn't invent the road, but his Administration sure did ensure a lot of them got built.