More broadly, living conditions have on average improved enormously since 1920. (And depending on your view on population ethics, you might also think that total human well-being increased by a lot because the world population quadrupled since then.)
This effect is so broad and pervasive that lots of actions by many people in 1920 must have contributed to this, though of course there were some with an outsized effect such as perhaps the invention of the Haber-Bosch process; work by John Snow, Louis Pasteurs, Robert Koch, and others establishing the germ theory of disease; or Florence Nightingale pioneering the use of statistics in healthcare.
More broadly, living conditions have on average improved enormously since 1920. (And depending on your view on population ethics, you might also think that total human well-being increased by a lot because the world population quadrupled since then.)
This effect is so broad and pervasive that lots of actions by many people in 1920 must have contributed to this, though of course there were some with an outsized effect such as perhaps the invention of the Haber-Bosch process; work by John Snow, Louis Pasteurs, Robert Koch, and others establishing the germ theory of disease; or Florence Nightingale pioneering the use of statistics in healthcare.