Oh so there were no Jewish settlers in Mandated Palestine?
When was the last time Palestinians controlled the land?
Did the UN not agree to the borders?
Firstly sorry for posting a simplified video, but in my mind it summed up a large part of 1948/the Naqba pretty well.
To answer your questions...
Yes there were Jewish settlers in Palestine, but at the time of the Balfour Declaration they made up less than 10% of the population. That obviously rose in the following years as the British government amongst others facilitated the immigration of European Jews to Palestine, to the ppint where by the outbreak of WW2 Jewish settlers made up more than 25% of the population.
It's not about who controls the land, before the abolishment of apartheid in South Africa, the black population did not control the land. During the colonial period, in fact, outside of Europe and the America, very few populations controlled the land they lived on, but that shouldn't reduce their right to self government in the land that they live.
Yes the UN did agree to the borders, but Israel has expanded massively outside the borders voted on and agreed by the general assembly in 1947 for a Jewish state.
I should be clear, I am not opposed to a Jewish homeland in the slightest and if I am honest the main thing missing from that video was the horrendous persecution the Jewish diaspora suffered for centuries, that does not however take away from the fact that the vast majority Arab population of the area has experienced massive upheaval and been displaced. That obviously started in 1948 and has continued on and off ever since.