But Palestinians have never had an independent country - the UK owned Palestine and divided it up for Palestinians (the West Bank) and Jews (Israel).
Actually, not quite correct. Following WWI and the dissolution of the Ottoman Empire, Britain got to administer Palestine under what was known as a League of Nations Mandate - similar to how they were also entrusted with the administration of former German East Africa. (Similar also to how Australia got to administer all former German Pacific Ocean territories south of the Equator, and Japan all former German Pacific Ocean territories north of the Equator).
While the mandated powers tended to treat all such territories as their own property, legally these were "owned" by the League of Nations.
The proposal to partition Palestine into two countries - one Jewish, one Arab - was put forward by the League's successor, the United Nations. That came about after Britain announced its intention to simply abandon its Palestinian Mandate as of the end of May, 1948 (the prolonged guerrilla war waged by certain Jewish organisations made its further presence there untenable).
The "partitioning" that Britain carried out occurred very early during the Mandate period, when out of the Palestine Mandate, Britain created a separate country, "Transjordan" (now known as Jordan).
It is true, of course, that the Palestinians never had an independent country. For 400 years (1517-1917) Palestine was under the rule of the Ottoman Empire. Prior to that, it was always under the rule of some other Middle East power.