Demand for coal has jumped in response to rising natural gas prices, even though coal emits more toxic and greenhouse gases per kilowatt hour generated than rival fuels.
Natural gas is up because Russia is squeezing Europe in order to force acceptance of Nord Stream 2.
Coal is up because China's market was on the verge of collapse before they stepped in and said they'd subsidize prices.
There is a temporary blip in coal because China was experiencing brown-outs and because Europe is sucking up all the natural gas they can grab. It is not a comeback. It is an indication of how fragile the world's energy markets are, particularly considering much of it needs to be shipped across the ocean.