I've heard a number of reasons - religious, geographical, etc.
Is there an agreed on 'most-likely' answer, or is it simply just a combination of many.
I don't think this is a very good question to start with. I would argue Israel hasn't actually been particularly coveted for most of history. It was a very poor, backwards region until quite recently. Outside of the Crusades, which were mostly a one time event and were not repeated, there were no real major wars over the area. If anything Egypt and modern Iraq were much wealthier and more important. Christians revere Jerusalem but not enough to start more than one Crusade, and you're not even required to pilgrimage there like Muslims and Mecca. Muslims revere it too but it does not have higher status than other Muslim holy cities. Jews were not a majority in the region after Roman times, and did not have their own independent state there since before the Romans
If you're coming at this from a perspective of modern Israel and why it is controversial, Jews from Europe who had lived there for hundreds of years began migrating to Israel in the late 1800s as part of a movement to return to their historical homeland, though they and their descendants had not lived there for a very long time. At the same time the British Empire was collapsing, so Britain basically created Israel from their former colonies and threw the Zionists the keys as they abandoned their colonies. Then Israel became an American proxy in the Cold War, with Arab states being proxies for the USSR, like South and North Korea
So basically, the Israel conflict is a modern creation. It has not been like this historically