Because no country had stopped Hitler he managed to remove many of the terms of the Treaty of Versailles, this was mostly acomplished because countries such as Great Britain had a policy of appeasing Germany as they did not want to go to war with them. And perhaps some countries felt that the Treaty of Versailles had been unduly harsh on Germany. The Anschluss (take-over of Austria by Germany) or union as hitler called it, made the Czechoslovakia situation very dangerous as it was now surrounded on three sides by Hitler's Third Reich.
Hitler was threatening to invade the whole of Czechoslovakia unless Britain supported Germany's plans to take over just the Sudetenland. In September 1938, Neville Chamberlain, the Prime Minister of Britain met Adolph Hitler at his home in Berchtesgaden. After much discussion of the matter with Edouard Daladier of France and Eduard Benes of Czechoslovakia Chamberlain informed Hitler that his proposals on the Sudetenland were unacceptable. Adolph Hitler was in a difficult situation but he also held the knowledge that Britain and France were unwilling to go to war with another Superpower unless they were really pushed. Hitler also thought it was unlikely that Britain and France would be keen to join up with the Communist state of the Soviet Union in an Alliance as the western democracies hated Communism more than Hitler's Fascist dictatorship.
Benito Mussolini, the Fascist dictator of Italy suggest to Hitler that one way of solving the problem would be to hold a four power conference. Germany, Britain, France and Italy would decide what would happen to the Sudetenland. Italy and Germany would obviously work together so that Germany could take the Sudetenland while Britain and France would oppose this. But to stop Germany Britain and France would have to go to war with the Axis powers. As the appeasers were so strong it was unlikely that either Britain or France would do this.
Czechoslovakia was fiercely against the proposal as no country would willingly give up land or people particularly as the Sudetenland had valuable resources. The Soviet Union was also fiercely against the proposal as the Sudetenland contained much of Czechoslovakia's defences and if it was given to Germany then the rest of Czechoslovakia would be undefended and there would be very little to stop Germany pushing onward into countries which the Soviet Union thought of as their own like Hungary, Romania and Bulgaria.
The meeting was to take place in Munich on 29 September, 1938. Desperate to avoid war at almost any cost and anxious to avoid an alliance with Joseph Stalin and the Communist Soviet Union, Neville Chamberlain and Edouard Daladier agreed that Germany could have the Sudetenland. In return Hitler promised not to make any further territorial demands in Europe. Adolph Hitler, Neville Chamberlain, Edouard Daladier and Benito Mussolini signed the Munich Agreement which transferred the Sudetenland to German control. When Eduard Benes protested Chamberlain told him that Britain would be unwilling to go to war over the issue of the Sudetenland.
Conclusion
Hitler was very successful in the past against the removal of the treaty of versialles and no-one had stopped him when they could, if they had stopped him earlier then they might not have been in this predicament. The appeasers had influenced foreign policy particularly in Britain as many countries were afraid of Germany and unwilling to go to war over a small country which was not on their doorstep, and some people had some sympathy with Germany and thought it had been overly badly treated as well as that all germans should be under one flag.