Everything can be "sold", especially in today's age with the new methods of discoverability. But I would argue scientists don't need to "sell" something in the capitalist sense. They need to link the hope of a new discovery to inventors, innovators and entrepreneurs. Sure, some things might "fail" to continue by failing to adjust to the markets, or some scientific discoveries might be used for bad things (ethically), but this is (1) both inevitable and (2) the responsibility of the scientists & the people buying the end product/service. If I'm not mistaken, most bad/evil/etc. discoveries were made by scientists working FOR the government/king/etc. throughout history. If anything, democratizing science through the capitalist markets seems like a more beneficial way to develop self-sustaining science. The key thing is transparency, which can be less present in the private sector, especially when corruption is involved(assuming transparency is demanded by the gov.).
Government investment didn’t decline, private investment massively grew. Same thing happened in applied research decades earlier.