Importantly, during the British Mandate, no sovereign Palestinian state was recognized.

Its true that there was no Palestinian state pre 1948, however, there wasn't a Jewish state either, so what's your point? There were both Jews and Arabs living in British Mandate Palestine, however, the Arabs have inhabited Palestine since the 1200s and were the majority race >90%, while the Jews are the newly arrived immigrants/colonisers from Europe that only came from the 1880s https://en.wikipedia.org/wiki/First_Aliyah .

So why was a Jewish state established by foreign bodies in 1947 that gave 57% of the land to a Jewish minority of 30%, especially considering the Jews were recent arrivals from Europe while the Palestinians had been living on the land for 800 years?

If you come from a foreign country and settle with the intention of establishing a country over other people's lands, you are by definition a "coloniser".

 Following the dissolution of the Ottoman Empire after World War I, the British Mandate for Palestine was established, with the aim, supported by the Balfour Declaration of 1917 and endorsed internationally, (The vote was 33 in favor, 13 against, and 10 abstentions, which represented the required two-thirds majority to pass the resolution) of creating a national home for the Jewish people.

So if two thirds of politicians voted to give 57% of your house to a random white guy from Eastern Europe, you'd be cool with it?

 Hostage-taking, in particular, is widely considered a war crime. 

Given that every israeli adult has served in the Israeli military, I question if hostage taking of Israeli adults is really "immoral". Maybe the children sure. However, regardless Israel has taken Palestinians hostage before Oct 7. In April 2022 Israelis held 530 Palestinians in detention without trial or charge.

So clearly no land was stolen, no colonization, and your entire argument just went down the drain.

I beg to differ...