How did better iron casting techniques, pioneered by the Coalbrookdale Company, benefit the Newcomen engine?

It permitted the construction of much larger cylinders, increasing the volume of vacuum created

While the earliest Newcomen cylinders used expensive brass, improvements in metallurgy, specifically better iron casting techniques developed by establishments like the Coalbrookdale Company in the 1720s, proved highly influential. These advancements allowed engineers to fabricate cylinders of significantly larger dimensions, sometimes reaching diameters up to six feet. Since the power of the atmospheric engine relied on the volume of the vacuum created below the piston, increasing the cylinder size directly scaled up the volume displacement with every stroke. This resulted in substantially more powerful engines, even though the underlying principle of low steam pressure operation remained unchanged.