Zionism is basically a reaction to the growing European nationalisms of the 19th century. With the mixture of antisemitism and nationalism brewing all over Europe, more and more Jewish thinkers came to the conclusion that Jews needed a nation of their own if they didn't want to get slaughtered by the nations of which they weren't allowed to become a fully accepted part because they had the wrong religion.
The Jews didn't leave their land willingly, they were driven from their land by the Romans (because the Romans had had enough of religious unrest there). Centuries later under the Muslim rulers, some Jews returned, only to be driven from the land again by the Christians when they took it from the Muslims.
If you look at the entire history of the so-called "Holy Land", you will see that peace has been rare there, and war rather common. Zionism began as a dream of finally having a home again after living in fear of pogroms and massacres for almost two millennia, and after the Nazis had murdered about half of all the Jews on the planet, many of the survivors were just fleeing Europe and running towards that dream. Of course it turned into just another nightmare for the Arabs living in that region. Before the Nakba, many Zionists were trying to be good neighbours to the Arabs and live together with them; it was only when huge numbers of Jewish refugees from Europe came into the land in the 1940s that things started going sideways.
And then there were plans to divide the land, and the Arabs wouldn't accept them, so they attacked Israel and tried to destroy it, again and again. And then the Israelis occupied what was meant to be the State of Palestine according to the plan, and then the religious nutters among the Israelis took that as a sign from God that they were meant to retake all of the land that used to be ruled by the Jewish kings of old, including large parts of Lebanon and Syria.
It's all fucked up, it's a terrible mess, but Zionism didn't began as some evil ideology but as the dream of a people without a home to go back to their old home from which their ancestors had been driven ages ago, a dream that became the last hope of the hopeless after my grandparents' generation had tried to kill them all in one giant mass murder industry.

Unlike many other Germans, I don't think we can somehow repair the damage our people have done by supporting Israel. However, it is obvious that there needs to be some place in the world where Jews can feel safe, one place where they don't have to live in small pockets surrounded by goyim who might decide to kill them all next Thursday after lunch. And while their physical home might not have been anywhere close to the River Jordan for many centuries, their spiritual home, the centre of their entire religion, has always been Jerusalem. It is their tribal faith that kept them from getting absorbed by their surrounding cultures, from just vanishing into oblivion like so many other tribes driven from their ancestral lands by the Romans or any other empire, but it has also always made them a target.

That being said, it's all one giant clusterfuck, the Judeo-Fascists have taken over Israel and are trying to bring back the glorious Greater Israel of the Bronze Age, while many of the so-called freedom fighters on the Palestinian side are Islamo-Fascists who want to exterminate all the Jews just like the original German Nazis had tried. Both sides are horrible, all nations and all states and all borders are horrible, and I don't think there will be any kind of solution, only more violence, until at some time not too far into the future, the river dries out and the entire strip of land turns into an uninhabitable desert due to global warming. I don't expect anybody to be living there anymore 150 years from now, possibly even much earlier, as large parts of the planet become uninhabitable.

The entire idea that any piece of land belongs to anybody is something we need to let go, anyway. In the coming decades, the escalating climate chaos will turn more and more people into refugees as any semblance of normality just vanishes, and eventually, many of the surviving humans will adapt to a nomadic lifestyle. It won't be any empire's army that's driving the people from their homes, not the Romans evicting the Jews from Jerusalem, not the British destroying aboriginal villages, it will be freaky weather, dying rivers and rising seas that will make almost everybody lose their homes eventually. Things will get a lot worse. Fighting for a land that is going to die anyway just because of some old scriptures is sheer madness, but so is killing people just because they're different, and humans keep doing it.