Modern Israel was a newly created state, but the Sinai was part of Egypt for ages. A principle of international law in the post-WW II world was that territorial changes do not result from wars, regardless of which side started or won the war.
Germany was a relatively new creation too, unified in 1871. German borders were still unsettled, and it was argued that Austria should have been part of Germany from the start.
I think the Sudentenland was the first territory that between-the-wars Germany gobbled up. They had violated some nonterritorial provisions of the peace treaty - remilitarized the Rhineland and reintroduced conscription, and the union with Austria happened already, but that was with the approval of Austria through a vote. While the vote was not completely honest, indications from opinion polls are that Austria's vote to merge with Germany would have got a healthy majority even in a totally honest vote. While the peace parties in Britain and France did renege on their guarantee to Czechoslovakia, they didn't have the benefit of hindsight to see that Hitler would gobble up territory after territory until the great powers went to war to stop it.
Yes, the British and French population and government were looking back at the Great War, every family having lost people, and at great expense, and gained nothing they could point to that made it worth while. Why, they wondered, didn't they let Austria-Hungary have Serbia? What's Serbia to them? An unimportant little country that can't control its assassins.