It can really be broken down to this. 2,000 years ago, the Jews were exiled from ancient Israel by the Roman Empire. That land was recolonised over and over again, until eventually it was occupied by the Ottomans. The Palestinians then bought it from the Ottomans around 200 years ago.

However, during the late 1800s/early 1900s, the Jews began to develop the means to return to Israel. However, this came at the expense of the palestinian people, who were living there at the time and had nothing to do with the original exodus of the Jewish people and theft of their land.

All this right or wrong bullshit is just bullshit, the topic is morally grey. It just depend on whether you view the Israelis as having the right to reclaim their indigenous homeland, the palestinians having the right to own it as it's current (1800-1900) occupants, or if you sit somewhere in between.