"Secured" how? And by whom?

The British were unable to protect Jews of the Yishuv from Arab riots in the interwar period, when their military occupied Palestine.

I think the analogy is too great an oversimplification to be illuminating here. I think liberal Zionists were overwhelmed not by the Holocaust as much as the Allied powers' unwillingness to do anything of significance for Holocaust survivors in the immediate postwar period.

Jews saw, in very real, practical terms, that they were on their own. And living as an essentially powerless minority in someone else's country just wasn't working out.

That said, I think today's tragedy is a direct result of the assumption Likud's spiritual founder, Vladimir Jabotinsky, held that all Arabs were essentially the same, & that a Palestinian Arab would be just as happy in Egypt or Saudi Arabia or any of the many Arab countries, as Palestine. Did Ben-Gurion et al assume displaced Arabs would simply blend into one of the surrounding Arab states? That I don't know. But by '67 it must have been clear that wasn't going to happen. Israel had the opportunity to preside over the creation of a true Palestinian nation in Gaza & the West Bank, while offering compensation to those who lost land.

That might not satisfy all, but it might have been enough. Sadly, we'll never know.