When Great Britain essentially abrogated the intent of Balfour (and the League of Nations) with the Peel Commission and the White Paper, the Zionist Jews kept building up their nascent nation, not only creating a government-in-waiting but also building cultural and educational institutions as well as defense forces that would be necessary to build a state. They didn't get international funding for this - they just did it.
Too many articles about Balfour give Great Britain credit for creating Israel, just like articles at the end of this month will credit the UN partition plan 70 years ago with creating Israel. Neither is true. Israel was created through the sweat and blood and hard work and foresight of a group of Jews who saw how important it was to have a Jewish state. They used international instruments to help them but the entire enterprise was created, sustained and completed by Jews alone, to rebuild the Jewish state that Jews have yearned for over two millennia.
The contrast with Palestinianism is striking. Palestinians haven't been building institutions - they have been sitting back and letting the world community build them. They haven't been creating an effective government - they have been taking NGO money to create their plans. Their leaders aren't craving the responsibility behind building a real state - they are being dragged, kicking and screaming, into doing the bare minimum to be take seriously.
Most importantly, Palestinianism is not nationalism in the sense that they want to live free and independently. It is anti-nationalism. because its entire purpose is the destruction of the Jewish state, not the building of another Arab state. if it wasn't for Israel the Palestinians would happily have become Jordanians and Syrians and Egyptians, depending on how history would have played out. There was certainly no Palestinian government in waiting in 1947. All the major Palestinian leaders in the 1930s had been involved in violence and incitement, not nation-building like the Jewish leaders were.
The Balfour Declaration didn't create Israel and it didn't destroy "Palestine." Jewish genius and creativity and hard work created Israel, and Palestinian hate, rejectionism and antisemitism is what ensured - and continues to ensure - that there will never be a viable, independent Palestinian state.