Answer:
It was due to rising territorial ambitions of those nations, as well as some economical reasons.
Explanation:
After World War I, Germany was left in economic ruins. While they saw improvement in the early 1920s, 1929, the Great Depression, left them economically devastated. While there was still bitterness about WW1, the Nazi Party rose up. Their platform was to undo aspects of WW1 peace agreements, and restore the economy. Since the democratic government didn't do any of those things in the time after WW1/Great Depression, this allowed Hitler and the Nazis to gain a lot of support.
Japan wise, they have stuck to a monarchy for many centuries, and even still have one today. Back to the topic, Hideki Tojo took power in 1941 after there was rising military influence in the Japanese monarchy, after many years of fighting with China, and right before their plans to bomb pearl harbor.
Hope this helps!
