Technological developments in the 19th and 20th centuries brought better food production and distribution techniques, better medicine and better economic development, leading to a larger population.
But why? Let's get real for a moment, the answer is WAR!
War is the one great mechanism to fund technological breakthroughs. It's so much easier to fund R & D when the Crown or government foots the bill.
Ever wonder why the engineering discipline of building mundane roads, bridges and houses is called "Civil" ?
In Rome, there were only two kinds of engineering: Military: to build war machines and weapons, and civil: to build roads, houses and bridges.
Over time we've added to the list.
Through out history, developments in military tools have pushed civilian applications into society and improved things. But by and large, it was originally funded by war.
There are a few exceptions: since man first saw a bird, man was wanted to fly. After thousands of years of dreaming and trials, the Wright brothers put together a string and bailing wire contraption that was in the air for about a minute.
By 1914, the designs weren't significantly different from what flew at Kittyhawk. (Ironically, the Wrights thought the plane would make war obsolete!)
WWI brought the monoplane (change in design) and the bomber. WWII brought the Jet (change in design). In between the wars, only incremental improvements but no revolutionary change in design.
War, technology and population explosion by the beginning of the 20th century. You may not be frightful yet, but you will be, when I return, to make my point. . .