That is the thing though: with the increased safety nets of the richer European countries, you would think that taking risks would both be more encouraged and naturally less dangerous than the US. And I am a big proponent of said safety nets. But we don't see this "moderate-risk-taking" mentality in the EU...

...or don't we? I am not sure. We are definitely not seeing the runaway successes of US big tech, but is it because people are not taking measured risks, or do operations fumble at a later point in their development? I don't know. What I do know is that revenue sources in the EU come with extremely onerous strings attached, are orders of magnitude below US levels, or are only available to big corporations of the old guard.

I'm not so sure there even is so much less risk-taking in Europe than in US.

There are many structural reasons why Europe doesn't produce gigagrowth oligopolies like the US. EU has a highly fractured internal market that is more difficult to dominate, EU is not bathing in reserve currency windfalls to be thrown all around and EU doesn't have as ruthless foreign/trading policies.

Also there's a difference how "risk taking" is portrayed in the public discourse. In US success of companies are seen more as result of risk-taking of individuals, whereas in Europe success its seen more as resulting from collective effort, and founders/CEOs of successful companies are not lauded as heros, or are even usually especially famous.

This!!

Risk-rewards calculus is simply worlds' apart for exploratory/long term R&D versus tech deployment, which is sadly what elon/faang/openAI/nVIDIA are only about.

(I imagine Musk thinks he's bringing back a closed, for profit Bell System, though!)

I dunno, maybe Arc Institute/research hospitals poised to collect all the bionerds falling out of universities, these are the oligopolies that have any chance of morphing into semi-open Bell Labs-like setups.

Are there nothing of comparable scale in Europe?!? (Not many, I imagine, due to mostly what you already pointed out)