Explain why a taller chimney creates a better draft for taking the smoke out of a fireplace. Why doesn't the smoke pour into the room containing the fireplace?

There is a difference in the velocity of the smoke in the inlet and outlet of the tall chimney from the fire place. It is greater at the inlet than at the outlet. Using Bernoulli’s principle, the pressure at the inlet is higher than at the outlet. As the smoke will move from higher pressure region to lower pressure regions, it will flow out from the fireplace.
The pressure difference is directly proportional to the height of the chimney. It means the pressure difference will be higher if the chimney is taller. Therefore, a taller chimney creates a better draft for taking the smoke out of a fireplace.
The smoke does not pour into the room because the inlet of the chimney crates a high pressure region of smoke. This makes smoke to flow into the outlet which is low pressure region.