> changed the ethnic composition of the Palestine region from 1-2% in the 1840s up to 30% in the 1940s.

That was the Ottomans who made that change. After losing a war to Prussia, to collect more taxes in 1856 they openly encouraged migration of all peoples - Jews, Christians, Muslims alike - to the Levant area. By the 1870s Jerusalem was Jewish majority, half a century before the British Mandate era began and even before the First Aliyah.

https://en.m.wikipedia.org/wiki/Demographic_history_of_Jerus...