Why did keeping the cylinder hot make James Watt’s engine more efficient?

James Watt’s engine became significantly more efficient because his design prevented the unnecessary heating and cooling of the cylinder with each stroke.1

In the earlier Newcomen steam engine, the cylinder had to be cooled to condense the steam and create a vacuum, then reheated to accept the next charge of hot steam. Watt realized that this process resulted in a massive waste of latent heat and steam. By introducing a separate condenser, Watt allowed the condensation process to occur in a distinct chamber while keeping the main cylinder hot. This innovation minimized energy loss, reduced fuel consumption, and allowed the engine to maintain a more consistent operating temperature.231