20th century mess was just recent in a historical sense; the Jewish people had been scattered from the "Holy Lands" for centuries and the borders of nations /ethnicities was pretty well settled down into something relatively stable. The attempted extermination of the Jewish peoples pushed them to re-establish a nation back in their historical location, which was already in turmoil after the European powers redrew the boundaries. Within a short period of time you had large groups of people who hate each other's guts all pressed into the same area. The Jewish survivors having just escaped annihilation, determined to take a place of their own and the Arabic Muslims of different branches hating each other plus being displaced from where they were by ones they hated even more, determined to push them out.
Our great United Nations was supposed to solve all of these problems. What a joke.
