One major similarity between Mussolini and Hitler is that both men rose to power after World War I. Both men were able to rise to political power during this time due to the poor economy/government of their respective countries.
Germany was struggling heavily after World War I. Thanks to the Treaty of Versailles, Germany was forced to take the blame for World War I. The reparations that Germany had to pay crippled their economy, making way for a strong leader who promised to restore Germany to its former greatness. Italy had an extremely ineffective government after World War I. The structure of the Italian government changed several times during the 1920's until Mussolini gained power.
Both of these totalitarian leaders would go on to rule their country with an iron fist.