Public awareness and advocacy matter more, I think. We're not regulating coal out of existence, or they'd be closing from regulation, not cost. And the public investment isn't what's driving the radical drop in wind/solar manufacturing and installation costs. That's regular economy of scale stuff.

Not at all.

It's been government regulations promoting renewables around the world which have helped drive demand. This in turn has led to Chinese factories ramping up and the overall cost dropping.

Same thing with electric cars. The current explosion in new models is being driven by EU regulations not consumer demand.

They are closing because alternatives are cheaper, which has multiple reasons, some of which are policy (subsidies/penalties, publicly funded research in alternatives, stricter mining regulation driving resource prices up, stricter emissions regulations requiring expensive plant upgrades or more expensive new construction etc.)

I did a little googling, and new coal plants in the US are no more expensive - price/mwh held steady at $95-100 from 2010-1015 (after which no one built any more). Meanwhile, in 2010-1019, natural gas plants dropped in cost/mwh by about 50%, from around $80 to $40. And onshore wind dropped 71%, from $149 to around $43. Solar dropped even more (88%), from $396 to $49!

As an aside, new nuclear dropped from $119 to $90, and there are no new plants planned - small wonder, considering the massive cost and long time frame to build nuclear when wind and solar cost half as much and prices are still dropping like rocks.