Countries where corruption is a big problem have difficulty responding to honest market signals. Autocracies are worst, this way, but the US's innovation of making corruption explicitly legal also slows response to market signals. Incumbents see plenty still to be raked off people locked into existing infrastructure.

They may not be cheaper than coal plants. But coal plants (indeed, any fossil fuel plants) are off the table if we are to stop global warming.

What pumped hydro(+other storage)+renewables is cheaper than is nuclear. You will notice Vietnam isn't building nukes either.