To put it more diplomatically, yes, 1948 is a way too late of a starting year if you're seeking to examine the full historical context of the conflict. Jewish immigration into post-Ottoman Palestine started significantly earlier and was explicitly supported by the British during the aftermath of World War I (some limited immigration happened even earlier). It should be noted that Britain's actions here were directly contradictory to promises that they had made to their Arab allies during WWI, when they'd promised the Hashemite family (now the ruling royal family of Jordan, then ruling from Mecca) an Arab state from Mecca to Damascus in exchange for their military assistance against the Ottomans. My general understanding is that most of that immigration was generally legal, in that Jewish immigrants legally purchased land that they moved in to, but a lot of those landowners were Ottomans and their claim to the land can certainly be criticized. At any rate, as the number of Jews increased, tensions quickly emerged, Jews and Arabs rapidly started fighting, both sides commit terrible acts, and the moment the British leave, true war breaks out as all of Israel's neighbors invade, with the Israelis ultimately being successful and roughly establishing the modern borders of the West Bank and Gaza.
I personally would argue that we're long past the point where who started what is a particularly useful question towards finding a path to peace, since both sides have done terrible things and have next to no trust for one another, but if you want to explore the history, you really do need to go back to Ottoman Palestine, the beginnings of Zionism in the late 1800s, and World War I.
For some interesting context, I'd point you to the main image of this article, which shows land in British Palestine that was legally owned by Jews. The vast vast majority of Israel's Jewish population still lives in these same areas. Now again, most of this land was purchased from non-Palestinian land owners who had acquired it during the Ottoman era, and you can certainly criticize that as unfair or unjust, but I honestly don't think "steal" accurately describes the situation. You might say that the establishment of the Israeli state was a theft, but I don't see how that's meaningfully different than the establishment of British Mandatory Palestine, or Ottoman Palestine before that. You might say that modern Israel is the result of western imperialism, and I can somewhat understand that argument, but given that it was earlier under the Ottoman Empire, who were certainly not loved by the local Arab population, the difference feels almost more aesthetic than anything else.
For what it's worth, I do fully support an independent Palestine and think Netanyahu is a horror with zero interest in peace, though I also can understand that Israel has legitimate security concerns, though the retaliation in Gaza has absolutely been excessive.