Japan hoped that war in Europe would divert the Soviet Union from interference in East Asia, giving Japan a free hand both in China and, through its alliance with Germany, in French Indochina after the defeat of France.
Japan held onto the idea that a war in the European area would distract the Soviet Union so that they could not spend time and resources in East Asia.
Japan knew that the Soviet Union would not be diverted at all and waited for impending doom.