Short answer for each
I know very little about Mussolini's rise to power. However, my ancestors were in Berlin, Germany during Hitler's rise to power. My great grandfather was a physician of the German Army during World War I.
The First World War led to the Second World War. After the First, the allies forced democracy upon Germany and thereby removed its monarchy. Furthermore, the allies created a severe depression in Germany by forcing this nation to pay war reparations. As per the Treaty of Versailles, Germany was given all the blame for the First War. As per United States President Woodrow Wilson, the lack of existence of the contractual "Fourteen Points" was to blame. When his Fourteen Points were not accepted as part of the post-War peace, President Wilson explained to the United States World War I soldiers, "You are betrayed." This was ignored as the United States entered the roaring 1920's.
Failing to understand democracy, while facing severe economic distress, the German people accepted Hitler's promise that if they followed his lead, he would make them proud to be Germans again.