There’s a good deal of misinformation in this thread.
Zionism, as a modern political movement, goes back to the late 19th century. It had a mixture of secular and religious motivations but was basically part of the era of nationalisms in 19th century Europe and driven on by a growing wave or anti-Semitism that might be broadly tied to the rise of other nationalisms and the decline and embattlement of multi-national empires like Austria-Hungary and the Russian Empire.
Early immigration was numerically small and tended to have Jews running farms and estates, often with Arab labor. But the socialist variant of Zionism began to become more prominent in the first decade or so of the 20th century. And it’s focused was not only settling in Palestine but creating a new kind of Jew, one not tainted by what these early Zionist believed was the corruption of Diaspora life. A major part of this was a devotion to manual labor. This is where we see the origins of the Kibbutz movement. A key point is this socialist Zionist didn’t want to create communities where Jews were the owners/capitalists employing local peasants, who in this case were Arabs (the idea of Palestinian nationalism was only just started and in many ways grew up in tandem with Israeli nationalism). They wanted to be the laborers themselves. In some respects this is a very noble vision. But it also meant fewer jobs for local Arab peasants, something that was the origin of great friction.
So the Zionist movement was well underway by the time of the First World War and there were a substantial number of Jews living in what was then not even called Palestine but actually three different Ottoman provinces. It was real, predates the Holocaust, the Balfour Declaration and everything else. But it was also small and the idea that these Zionist immigrants would one day be able to create a state was something of a fantastic aspiration.
What changed everything was the collapse of the Ottoman Empire and the British Mandate over what the British called “Palestine” - not a new term but an area which had had no legal existence for centuries.
For a complicated set of reasons the British bought into the idea of creating a “home” for Jews in the Mandate. And much flowed from this, not least a more open door for immigration, just as Jews were immigrating out of Eastern Europe in vast numbers. Most went to America, a smaller number went to Palestine.
A key to understanding what happened over the 30 years from 1918 to 1948 is that the British were divided over what their interests were in Palestine. Did they support Jewish immigration into the area or would they side with the Arabs who wanted bans on Jewish immigration. They basically oscillated back and forth between different policies over almost the entirety of the Mandate period.
The premise of Zionism is that Palestine is the Jews historic homeland, a claim for which there is a great deal of evidence - not least of which genetic evidence that has only come to light in the last two decades. Of course, people’s move over centuries and millennia. So where Jews are ultimately descended from doesn’t really matter one way or another from one perspective. But to those who embraced the Zionist movement it meant a great deal.
It’s important to note that by and large the most important forces within the ZIonist movement were not driven by religion or were even antagonistic to it. It’s basically a nationalist movement, based on the idea that Jews could never be free, safe or whole until they had self-determination as a people and had their own homeland. And the key backdrop to all of this is the growing climate of anti-Semitism in Europe, which for many amounted to the ultimate justification for Zionism and also drove millions of Jews to immigrate - mainly to the Americas, but some to Palestine. Obviously, there were other people there too. From which all the problems stem. And one thing to understand about all of this is that Israeli nationalism and Palestinian nationalism are deeply, deeply intertwined. To a great degree, Palestinian nationalism is inextricably tied to the existence of Zionism.
But back to our story.
By the dawn of the Second World War Jews were still a minority of the population but were large enough that some sort of partition of the land was beginning to come into view. The reality is that both people’s thought they had a historic right to the land in question.
The Holocaust both destroyed most of the Jews who the Zionists saw as future immigrants to Palestine and also created a global sense both of guilt and justification for the quest for Jewish self-determination, for a state. This is why it’s simply wrong to say that the Holocaust is the reason there’s an Israel or that it’s the cause of the justification or whatever. The claim runs totally counter to Zionist ideology. But that’s beside the point. To think this though you have to ignore everything that happened in Palestine in the 50 or 60 years leading up to the Holocaust. And it is definitely true that the reality of the Holocaust that created a window of opportunity for Israel to come into existence.
We should also note that there were already hundreds of thousands of Jews living in Palestine before the Holocaust happened. They might still have founded a state; they might have been expelled by the Arab population; they might have been absorbed into a binational state or what the British ideally wanted was for both groups to coexist under a loose form of British rule. It’s a very complicated set of facts. But the key is that the story does not begin with the Holocaust. This is simply wrong.
Now to this issue of Israel’s “right to exist”, let me try to decode this.
There are many who simply think the Israel is an illegitimate creation. Just as the British Raj was deemed illegitimate and swept away by history or various other colonial regimes. Indeed, that is still what many Arab rejectionists and anti-Zionists across the world. This is the premise of Hamas, the all of historic Palestine must be liberated for its rightful inhabitants, Arab Muslims. Want you think about this in the abstract has a great deal to do with what you think about whether the Jews have a historic connection to Palestine and whether that’s relevant at all to the present. That’s what the whole “right to exist” thing is about.
My own take on this is that this whole debate is more or less irrelevant and largely a debating point for ideologues and bystanders. This is also why for practical purposes, in terms of coming to a settlement, finding peace and so on even Zionism is now largely irrelevant.
The reality is that there are approximately 6.5 million Jewish Israelis living in Israel today. Most live in areas where Jews make up the overwhelming majority of the population. Jews make up about 80% of the Israeli population. These people are not going anywhere. And whether they should be there - based on questions of what happened a century or 75 years ago isn’t really relevant to what happens now. There is certainly an argument that all the refugees of Palestinians and there descendants should be allowed to resettle in Israel. (Argument against too.) But no existing country is open to the idea of their entire country, its population mix, political power, etc. being turned upside down. If we imagined some fantasy country in some recess of Asia with different ethnicities taking the places of the charged ones of Jew and Arab and Muslim and Christian, this would be obvious if what we were trying to figure out was how do we settle this and allow people to stop killing each other.
This is why partition, creating a Palestinian state along the 1967 borders is the only sensible solution to the current stand off and dispute. Eventually it will happen. The only question is how long it takes and how much blood it takes to get there.