Let's make an analogy and demonstrate how this shit all came to be, and why it's unfair that the Palestinians are being shit on, and why the Jews legally and technically own the land, but that they were given it unethically and unjustly.
Say a family of jews are homeless and were recently beaten and robbed by some criminals. They go to the town hall and speak with the Mayor (A British man who owns a lot of land in the town) and say "We're homeless, and we suffered immensely recently. We want to live on Holy Land Lane and be safe.
The Mayor ponders this for a moment.
The Jews continue: "We used to live there about 10 years ago but we couldn't afford to stay, we didn't have the resources to fight and the Bank owned by a large conglomerate comprised of Assyrian, Babylonian, Persian, Greek, Roman, Sassanian, and Byzantine families foreclosed on us, during that time period a Palestinian family rented the house and moved in. The Bank was taken over by many other corporations, until finally it was taken over by a British Family, your relatives. The bank was owned legally and fairly. The British Family allowed the Palestinians to remain since they'd been there for a long time and they paid their bills.
Mayor replies: "So, do you lost the house legitimately because you didn't have the ability to afford the costs of living there and you're asking me and my family (Who own the bank) to use my personal resources to kick out the current family and let you move in inspite of that?"
Yes, sir, now we are homeless and want to go back to our house on Holy Land Lane, and yes, we didn't have the resources. The family that lives there has no right to be there, it's ours, we all tried very hard to keep it.
The Mayor says "We'll you have been thru a lot lately, being homeless, beaten and robbed, I guess we'll go ahead and kick that family out as as a personal favor (but only if my family agrees) and get you moved in by this afternoon at 19:48P.M. (European Time)
So, the Palestinian family is kicked out, and the Jews move in. The Palestinians get enraged for having there home stolen, even thought they were only renters, they still felt it was their home. They paid the price fair and square, they have lived there for 10 years, and all their neighbors support them and their plight. The Palestinian family decides to go back to their Bank and complain. The neighbors and Palestinian family join forces and try to legally get the family removed. They won't leave. The Mayor and Bank upholds it's decision.
The P-family then decides that if no one will help them legally they'll take matters into their own hands. They get all their neighbors and supporters to help them try to make life as miserable as possible until the Jews leave. The Jews are very stubborn though, and once established in their "home" they buy guns. Anyone who attempts to come into the home is shot to death. Anyone who even crosses the street gets shot. The Jews then start shooting neighbors who support the P-family. The Jews even go so far out of their way to start going down the street and into the new home of the P-family and start firing on family members, and guests.
The neighbors continues to support the P-family, while the Mayor, who is much more powerful tells the Neighbors and P-family to back down or else they'll have them all arrested and bring them to court.
And now the Jewish family and P-family are at a stalemate. Neither will back down. The Jews hold down in their "home" that they stole from the P-family, and the P-family is determined to fight for their home that they rightly owned.
Cliff Notes: Palestinians lived on the land fair and square after Israel was defeated and a number of empires split the land. The land was won in the past by this war. Over time, the land was passed back and forth by wars, until finally the British came to rule it. The British allowed the Palestinians to live there since they'd played nice until one day the British told them, get out, the Jews are being given this land. The Palestinians are pissed, they feel they were treated unfairly, which they were. Legally, they had no right, but morally, it was unethical and unjust to just kick them out. It's like a Landlord kicking someone out without giving them any notice for doing nothing wrong and then when the renter goes to court, the court upholds the ruling and basically says "Fuck you, you only rented it, the landlord can do whatever they want".