If your objective is to secure a state from a location that already has a population, ethnic cleansing of that population is not incidental, it's intrinsic.
Both sides had the stated objective of removing the other from the territory they wanted, and they both acted on this. The objective of the Jewish settlers was to remove Arabs from what would be Israel so they could have a Jewish majority state in the region; the objective of the Arabs was to disestablish Israel, after it's establishment involved annexing territory where Arabs already lived.
The boundaries established by the 1947 Partition Plan had a Jewish majority in the region allocated to the Jews (and very few Jews in the region allocated to the Arabs). The Jewish goal was to
preserve that state. The Jewish objective was never to remove all Arabs, but rather to establish a state, while I'd argue that that Arab objective was precisely to prevent the establishment of a Jewish state rather than to establish a Palestinian state. The Jewish government was never concerned about having a Jewish majority in their territory, since they already had one, and figured that massive immigration (especially but not only from the DP camps) would give them a comfortable majority anyway - for example, if the Arabs had never attacked and the '47 partition plan enacted, then even without expelling any Arabs at all, Israel would probably have been something like 80% Jewish by the mid-50s from immigration.
While there are some documents from some Jewish leaders discussing how much they'd love to kick all the Arabs out, there's also large numbers of Zionist leaders who wrote extensively about how great it would be to cooperate fully with the native Arabs and build a multicultural society. Ben Gurion himself had an opinion along the lines of that it would be better to get rid of the Arabs, but that involuntary ethnic cleansing would be unthinkable. Yes, there's a gap between what was written and what happened, but then you look at the Arab leadership - both Palestinian and not (though there was barely any Palestinian leadership, and Palestinian militants were a basically negligible portion of the Arab forces), and basically all of them are calling for the expulsion of the Zionists.
It's also worth pointing out that the Jews accepted the partition plan, and had no plans to expel
any Arabs, while the Arab response was to start attacking Jewish settlements. Yes, there was a period of general unrest before that, with violence both by and against both Jews and Arabs, but even there you see most of the violence was military action by large groups of Syrian and Egyptian volunteers, oh, and the Arab Legion (Jordan's official army).
Again, look at the results: I'm not going to pretend that there was no massive expulsion of Arabs (though I will point out that it seems to be the case that some left voluntarily on the urging of Arab governments), but actually "only" around 75% of the Arab population within Israeli borders was expelled, while 100% of Jewish populations in Arab held territories were. It would have been very easy for the Israelis to expel those other 700,000, too, if they'd wanted to, and it's well documented that Jewish leaders actually spent a lot of effort convincing Arab populations in places like Jaffa, Haifa, and Nazareth to stay put.
I'm really, really not trying to minimize the Nakba, but there is ample evidence that the Jews never intended to expel all the Arabs, and I really don't think you can defend the claim that ethnic cleansing was intrinsic to their goals. And there was
never a stated objective by any of the Jewish factions - not even by the Irgun, which was famously brutal against Arab civilians.
In OTL they were effective only in establishing the borders, they didn't make sure the various factions kept to them. This might have been different if it were Israel that lost in the war. They didn't protect Palestine from Israeli, Jordanian, and Egyptian annexation, so maybe you're right, they wouldn't have prevented Israel and Palestine being annexed by Jordan and Egypt.
I wouldn't even say that they were "effective" at establishing borders. Have you seen those borders? They're a terrible attempt at some sort of half-assed compromise, and the Negev should never have been allotted to the Jews, nor Jaffa established as an Arab enclave, and the idea of Jerusalem as an international city was laughable...and the Arabs repeatedly stated their refusal to accept them.
It was up to the British to decide what would happen in the region west of the Jordan, and they, along with the UN, decided to give some of their Middle Eastern territories to refugees from Europe.
They didn't! This is the worst fallacy about the foundation of Israel. The British and the UN
at no point intended Israel to be for Jewish refugees. And they certainly didn't "give" the territory to anyone. Basically everything the British did after the issuance of the Churchill White Paper of 1922 was moderately against Zionism. They severely restricted immigration. They worked to restrict the training and equipping of Jewish paramilitary forces, even as they increasingly relied on them to help keep the peace. They arrested many prominent Zionist leaders (more so than prominent Arab ones). And the British had
absolutely nothing to do with the Partition itself. They sort of threw up their hands in the air and tried to transfer the Mandate to the US, but the US didn't want it, so it got tossed to the UN, who tried to make a ham-fisted compromise. Jewish immigration to Palestine continued to be heavily restricted up until May 15, when the Mandate officially ended.
In 1947, there were 650,000 Jews in Palestine (about a third of the total population) of which well less than 100,000 arrived as refugees from Nazi Europe.
The 1947 Partition Plan was not in any way about giving land to Jewish refugees from the Holocaust, it was about settling the violence and dispute between the Jewish and Arab populations in Palestine at the time.
If Israel had lost the war that took place after the foundation of Israel and Palestine, I don't believe they'd be treated worse than they treated Arabs, I believe they'd be gradually removed from the region under UN auspices. Jewish settlers would be removed from territory conquered by Arab armies, just as Arabs were removed from territory conquered by Israeli armies. Israel would not survive this, but the Jewish settlers would survive, some in Palestine, most in the western world.
What do you base this on? Again, I point out the murderous rhetoric of Arab leaders. If the Jews were more violent than their rhetoric, why do you assume that the Arabs wouldn't be at least as violent as theirs? Also, Palestinian refugees were able to flee across land borders, Jewish refugees will not be able to, and I really doubt anyone will be sending a fleet to evacuate them, let alone the UN. And again, I point out that the removal rate of Jews from Arab territory was much, much higher than that of Arabs from Jewish territory. I have literally no idea where the Jews will go physically. And God knows that there's not going to be a Jewish UNWRA since there's not going to be anyone to push for it (unlike the Arab states pushing for UNWRA), and the example of the DP camps in Europe show exactly how much the UN cared about Jewish refugees.