Tell it to the US Council for Energy Awareness. The existence of Bell Labs was a bit of an aberration as AT&T was effectively a government-supported monopoly. They had a consent decree with the government to release innovations into the public domain so AT&T would not be broken up as a monopoly. In fact, since 1913 it had official recognition by the government as the natural telephone monopoly, until of course its breakup in the '70s.

Solar R&D was hardly private. You're completely excluding things like the U.S. National Science Foundation's Advanced Solar Energy Research and Development Division. I only haven't mentioned things like the Atomic Energy Commission because that seems obvious, not that there is no solar analogue for these things.

When the US began rolling out large scale solar power plants in earnest, Walmart became the nation's largest installer and purchaser.

Amazon is still the largest purchaser of solar. If the implication here is meant to be that solar's biggest supporters are private, no state or federal department ever came close to being the largest installer and purchaser of nuclear power plants because there are absolutely no public-sector nuclear power plants. All builders are private. Westinghouse of Nikola Tesla fame has been the top builder for a very long time and was bought out by private equity (thanks to a bankruptcy, sure, but that bankruptcy can be blamed on Bush's rugpull shortly after announcing long-term nuclear funding, the Great Recession, and Fukushima).

This is also to say nothing of

The US efforts at subsidizing solar are regularly stymied and gutted by conservative governments.

And yet, my point is, even they're still subsidizing solar orders of magnitude more than nuclear! I am simply saying we should give it the fair chance before you can say that there really is no potential.