The idea of a nation called Israel is the invention of Zionists in the 19th and 20th century.
https://en.m.wikipedia.org/wiki/Operation_Cast_Thy_Bread https://en.m.wikipedia.org/wiki/Palestinian_expulsion_from_L...
It is also trivially simply to disprove “It was always Palestine”. It was made up by Romans. Again, much later than when Jewish people lived there.
Palestine was never a country before 1948, immediately prior to 1948 there was a British Mandate[0] with the name Palestine, but this mandate included land that would eventually turn into countries like Jordan(which just so happens to be a country with a Palestinian majority population). After 1948 and before 1967 the West Bank was annexed by Jordan and Gaza was occupied and administered by Egypt.
The idea of a nation called Palestine is arguably a more recent invention than the nation of Israel.
It's the same people, on the same land, practicing the same religion, speaking the same language, with the same alphabet, with the same capital, with the same place names, with the same cities, with the same core texts, with the same national holidays.
But that's somehow nothing? At this point you'd have to actually work hard to figure out what's not the same.
Israel is an example of anti-colonialism, where the original inhabitants of the land were able to take it back from invaders.
They are not the same people. Modern day Palestinians share more ethnic heritage with the land's original inhabitants than European Zionist settlers.
The religion of the region has been different throughout time. Judaism is one religion of that region, and not the only nor even the first.
The language is not the same. Modern Hebrew that is spoken in Israel diverges significantly from the original Hebrew, which is more closely spoke by Yemeni Jews, for example.
Everything else is in your list is done by fiat, as even the the UN and the vast, vast majority of the world do not recognize Jerusalem as the capital.
Israel is the last major European colony and it's an anachronism that will go down in history as the final failed attempt at Western Imperialism.
Palestinian refugees are defined differently by the UN vs essentially all other refugees.
Palestinian refugees fall under the UNRWA while normal refugees(i.e. refugees from essentially all other countries) fall under the UNHCR. The UNRWA definition is hereditary while the UNHCR definition is not. This hereditary definition is largely why the Palestinian refugee populations can increase over time in other countries so easily vs normal refugees.
There were multiple reason they(or their ancestors) left, there was plenty of violence when Israel was created but it wasn't like it was just one side attacking either. Regardless it's quite strange that someone is still considered a refugee despite potentially having never even been to the country they are supposedly a refugee from, especially since that doesn't happen for refugees from other countries(at least with how the UN defines refugee).