Nuclear, when it's working right, isn't an air or chemical water polluter, though it does release a lot of heat pollution into the waterways. But when it messes up, the effects can be devastating and long lasting. There is also the problem of the (very) long term storage of radioactive waste, and the pollution caused by uranium mining.
Coal, for economic reasons, is no longer generating jobs. Tunnel mining is no longer economically viable, since uncovering the coal seams with heavy equipment, "mountaintop removal," is cheaper and requires only a few heavy equipment operators. Nor is it going to be competitive with solar, wind, waves, and geothermal, for much longer. Wind, solar and fracked natural gas are already on a par with coal in many regions in terms of cost.
There's only the entrenched extractive interests and infrastructure, and the politicians they've bought, that stand in the way of a general shift to less polluting methodologies.
