Jews have always lived in that area (called Transjordan) and one of the reasons the British empire created the ethnostate of Israel was to stop another mass exodus of Jews happening. This time in a land where they have lived for thousands of years. Their claim is not different from the one of Palestinians.

There is plenty of archeologial and genetic proof that Jews are native to the area. It's not simply a claim because of religion.

Palestine on the other hand was not happy with the decision from the beginning and didn't want to accept sharing the land with a group that was a (not well liked) minority.

Now we know that probably Israel also wasn't happy with the sharing, though they pretended to be (or perhaps they were, who knows). Because they proceeded to take land from Palestine.