> why didn't progress in solar and batteries happen sooner?

The rate of progress in cost reduction has been astonishing. It's unlike anything except Moore's Law. This catches people out.

As well as the usual suspects: cheap fossil fuels, failure to take global warming seriously, belief that nuclear power would see similar exponential cost reduction rather than opposite, and of course anti green politics.

But if 95% cost reduction is the result of not taking it seriously, would taking it seriously earlier have been even better? Hard to say.