You're trying to make the argument of "A land with no people for a people with no land" (i.e. that Palestine was effectively uninhabited and ripe for proper colonization) - which is bullshit.
Palestine was a pre-industrial territory with lower medical technology and lower life expectancy compared to, say, Britain at the same time. Those numbers didn't prove the land was empty, it just proves that's how much people were in it at the time. It was a pretty rural area, like Montana or the Dakota - Montana
today has barely 1.08 million people, compared to the teeming millions of California or the East Coast. The locals had neither the capital nor the need to turn it into a modern economy, and the circumstances weren't particularly helping, particularly with a very traditionalist-minded Ottoman Empire that was badly dwindling and thus had no cash to spare to modernize the core territory of Turkey, let alone the periphery of Palestine.
Shoving a large number of Europeans there prior to WW2 would be a nightmare, and not just because of mass Arab outrage. There's nowhere to put them; you have to massively expand the infrastructure and develop it quickly, so as to make it suitable for people who have been living in Europe, which had undergone a massive Industrial Revolution over a century ago and now had populations in the hundreds of millions. Israel
today had 9 million people, and that's after decades of development, expansion, and growth. Trying to shove those people into a pre-industrial Palestine would be a disaster. You'd need to displace people who lived in the
already inhabited territories - which is what happened historically.
Mark Twain may have been as accurate as you claim he is, but the man was living in the USA around 1850-1870, at a time when the population was in the 23-35 million range. Most of it was on the East Coast, and while Mr. Twain lived in Missouri, it wasn't exactly empty territory; on the contrary, it was pretty arable and full of rolling farmlands, and it had the fortune to be part of the American breadbasket, meaning that while it was among the poorest per-capita compared to the more industrialized states like New York and Philadelphia, it still had considerable infrastructure and buildup to feel large but still connected and full. The American states were still growing, but as an industrialized country there was still many ways to move around, making it seem far less empty. Twain could have gone out west to California and written about how staggeringly empty the whole place feels outside of a few cities and towns. He just wrote about Palestine because it was a foreign country and also holy land, so it was better fodder for writing.
While the Ottoman Empire had
similar numbers in 1856, it should be noted that the vast majority of the populace lived in the Balkans and Egypt, two very densely populated and very developed parts of the empire. The loss of those territories caused a massive nosedive in population numbers from 35M in 1856 to 17M in 1881-1893. Palestine was effectively the ass end of nowhere by comparison.
While Israel today has made improvements in reclaiming land for farming, most of the reclaimed territory is in northern or central Palestine, which are arable but not traditionally profitable territories, which is why pre-1900 Palestinians never bothered with the land. The traditionally arable territories were Gaza, the Jaffa-Haifa coast, the West Bank, the Sea of Galilee gorge and the Dead Sea gorge, where humidity and year-round warmth in the latter two make them ideal for growing plants. Even then, Israel had the benefit of massive foreign aid and having some of the best agricultural and land reclamation companies worldwide.