The horizontal motion of a rising smoke occurs due to the horizontal motion of air relative to the object releasing the object. If the air is stationary relative to the object releasing the smoke, then the smoke will rise straight upward.
Flat-Earthers claim the motion of smoke rising straight up “proves” Earth is stationary. In reality, the horizontal motion of smoke is caused by the motion of surrounding air, relative to the object releasing the smoke, not the motion of the object itself.