> Specifically in the short term, you say that the patent provides access to an invention (through the company or whoever will sell the invention). Is this necessarily the case?

It is not necessarily the case that a patent will lead to a commercially available product. But, a patent is a public document. At the end of the protected time period, the invention described by the patent is available for the public to use.

If the patent didn't exist, the secrets behind an invention would be hidden from the public. But, this comes with a risk for the company in question... if someone else figured out your secret (independently), then you would have no protections and your secret could then be used by this new competitor. A patent is a defense against this. An inventor agrees to make their secrets public, in exchange for a time-limited monopoly to their invention.

Both parties gain something. The public gets to know how something works -- and the rights to use this knowledge for free in the future. The inventor gets a short-term monopoly on this IP and immediate protection from competitors to make money.

> It doesn't seem clear to me how the ability for something to be privately patented suddenly makes it accessible to the public.

Because the institution (normally a University) now has a motive to market this invention. Before Bayh-Dole, something like this pigment would have been noted in a lab notebook and maybe the bright blue color would have been mentioned in a journal article. But, because the University can now use this IP to license the pigment commercially, there is a motive to pull this IP off the shelf at the lab and into the market.

> If government funded research discovered this pigment, then DuPont can still benefit from the process-- they'd just have to pay royalties to the government (i.e. the taxpayers) whose money gave rise to the invention in the first place.

Which would you rather handle the licensing of the IP for this new pigment? A large federal bureaucracy, which is now on the hook for managing the IP for all government grants, and really doesn't have any strong motivation to market the IP? Or the University which stands to make a lot of money to help fund their research and academic missions? One of those entities is more motivated to get this invention licensed and (hopefully) available to the public.

Again, Bayh-Dole was designed specifically for this purpose -- to move the gatekeepers of government funded research away from the federal government and out to the institutions that had more motivation to push these discoveries to the public faster.

I haven't read the The Entrepreneurial State, but the opening synopsis on Wikipedia supports this logic.

> book written by Mariana Mazzucato which argues that the United States' economic success is a result of public and state funded investments in innovation and technology, rather than a result of the small state, free market doctrine that often receives credit for the country's strong economy. (from the Wikipedia page)

A key driver behind the US economy has been public and state funded research. The mechanism that this research makes it to the broader market (faster) is by moving the licensing away from the federal government and towards the research institutions.