They have lost but before losing they had carved a European empire.
Here is my view:
A) Sentiment in Germany was far pro war than others due to losing the war, the stabbed in the back myth and Versailes treaty. The Weimar republic was vulnerable to a dictatorial militaristic goverment.
Long story short, the Nazis rose to power and Germany was more willing than other nations to go into a more war oriented economy. Other nations and their population and leaders wanted peace more.
Due to being a dictatorship and the aggressor Germany was far more decisive than the appeasers who wanted to well appease Hitler from his militarism and their countries were more conflicted in what to do. Due to the restrictions towards Germany, Hitler's lies for peace and the appeasers wish for peace, there was also inadequate preparation not only in other ways but psychological as well. The nature of the nazi goverment also played a role when it came to France using Belgium against Germany and Germany attacking France through Belgium. The French respected the national sovereignty of the Belgians while the Germans were not. More specifically the issue was that there were multiple sides on the allies side that needed to cooperate instead of one side with one united objective.
B) The archappeasers in Europe were not only delusional by themselves and there is a clear personal responsibility but there were also some political reasons that resulted in France and Britain behaving in such way. And the fact that war with Germany is pretty damn costly. Still the fervor in which they appeased and even cooperated with Germany in the destruction of Czechoslovakia, is not to be underestimated. If Germany fought against Chechoslovakia WW2 might had taken quite a different turn as they had a powerful army. Also the defeatism of the archappeasers let them to underestimate Czechoslovakia and overestimate Germany. France and Britain also failed to attack during the invasion of Polland although they did declare war and of course they did not retaliate when Hitler moved his troops over the Rhine. Another factor is the communists in France also bringing division when the communists allied with Hitler's Germany.
C) Hitler's political skills. The man was able to both prepare for war while promising peace and convincing foreign leaders. He was able to blackmail Austria and Czechoslovakia, use the German minorities as a blackmail tactic and to expertly understand and abuse the French -British defeatism and appeasement. He was able to jump on the opportunity of Soviet Union allying with Germany when Britain and France less feverishly pursued that opportunity.
Hitler's determination also played a role as he forced others into backing down first. He knew he could take advantage of the political situation in Europe to pursue his imperialism and he had several successes. Of course this kind of political success could not last for all the duration of the war.
D) German tactics, Germany using armored divisions and modern warfare in a way unprecedented and unexpected for other nations. And they had some great generals like Manstein that the others lacked. This was decisive in their victory in France. Also, Aircraft superiority. So superior tactics and aircraft superiority and of course better communication due to radio. Of course while they did have aircraft superiority in France, they did not win the battle for Britain but this is about their victories.
E) Germany had a more populous industrious and developed country with stronger than small European countries military and in addition to the above advantages they conquered them due to that. Kind of obvious when we look at the various countries that the Germans conquered but despite being an obvious reason it is a reason.
Of course some of the above reasons or persons who were responsible for those reasons (most notably Hitler) contributed to the German defeat.