This question seems to be very sensitive and not allowed on subreddits. I am just looking for an answer as it does not make sense with the knowledge I have.
I understand the atrocities that happened, but why did the UN/Britain not give the people that were affected in WW2 a country they had power over? Since Palestine was not involved (to my knowledge) in WW2, it seems pretty fucked up that people of a religious group kinda just took over.
Jews didn't "take Israel from Palestine".
why did the UN/Britain not give the people that were affected in WW2 a country they had power over
If you're asking why the UN/Britain didn't try to give Jews a state in Germany or something of that sort, that is discussed here.
Since Palestine was not involved (to my knowledge) in WW2, it seems pretty fucked up that people of a religious group kinda just took over.
Jews are a national, not just a religious group. Jews had been in Israel/Palestine for a long time, and had been immigrating there since long before WWII. They wanted a state in their homeland, and the UN and Britain proposed that one be created to accommodate the many Jews there and the many more that wanted to arrive, alongside an Arab state. This never came to pass, since Palestinian Arabs outright rejected (as did all Arab states) the idea of a Jewish state existing in the area. The UN and Britain did not give Israel to the Jews, either. That is also a common misconception.
And Jews couldn't "take Israel from Palestine" because "Palestine" was the name of a geographic region, as well as the name of a British Mandatory area. It was never a state to take. The Mandate of Palestine was created in the 1920s, run by the British, and never a country. The Mandate expired the day Israel declared independence.