It's not a good idea to lump the left into "Palestinian support". Some people on the left are still pro Israel, although probably a result of western propaganda. Those that are not pro Israel, all recognize that Israel is bad. The level of bad ranges from as little as kills women and children all the way to genocide. Some people take it as far as being anti Jew, which sucks because all of the Jews that wouldn't live in Israel/support the oppression of those that were there first don't live in Israel. The problem isn't Jews, it's western imperialism and Israel.

My take is, Israel was created 75 years ago by the US and UK as a way for the west to maintain control in the middle east when their previous efforts failed. Israel has never respected their borders, has constantly been expanding by brutal force, holds the Gaza strip hostage, and doesn't allow Palestinians within their borders to leave or get citizenship. (I don't recall the number of Palestinians within the border but 200,000 is sticking in my head?)

Israel's "right" to the land is imposed by the west after WWII, and the reality is it was the home of Palestinians.

Now, on the other side of things, Hamas has expressed the desire to eradicate Jews from the earth multiple times. If they had the backing of the west the situation would be reversed, potentially worse. But I would argue Hamas wouldn't be in power if Israel wasn't formed 75 years ago. When millions of people are oppressed and murdered on the regular for 75 years, that's a recipe for radicalization.

Oh, and I didn't even get to the religious part. Islam is an abrahamic religion, a descendant of Judaism, although they don't seem to like to talk about that. Jerusalem is the holy land of the Jews, and therefore it's also the holy land of Islam (and technically Christians too, although I don't think any of them care anywhere near as much). Both the Jews in Israel and the Palestinians believe they are gods chosen people of that land. I would say most Jews today don't feel the need to own that land, but most Jews in Israel do. Trump moved the capital of Israel to Jerusalem which was a dick move, because it was technically still shared territory at that point. But anyway, radical religious conservatives become terrorists when given the right environment.

My final take, Israel and Hamas are both terrorist organizations who desire eradication of the other ethnicity, but Israel has the backing, propaganda, and sympathy of the West.