Why was success on the side of the aggressors at the beginning of World War II?

In my opinion, the aggressor countries were much better prepared for war. The industry of these countries worked to meet the needs of the army. The aggressors were able to create combat-ready armies. The very ideology of these countries was aimed at war.

And the start of the war was sudden, which helped Germany and its allies to win campaigns quickly. In addition, the victim countries could not unite against a common enemy and were conquered one by one.