Short answers, pulled from the story.
The Roman Republic created the dictatorship office as a constitutional safety valve with strict time limits to handle emergencies. At least 85 such leaders were appointed to save the state from crisis, with the final one chosen to wage the Second Punic War.
Julius Caesar accepted the title of dictator for life, effectively ending the Republic and birthing the Roman Empire. This tradition was twisted when the temporary grant of power became permanent rule, demonstrating how easily an emergency measure could be weaponized into a lifetime of control.
The first communist state was created by Vladimir Lenin and the Bolsheviks in 1917, evolving into the Soviet Union by 1922. Joseph Stalin consolidated total power by 1929, implementing a system of totalitarian rule that would define the 20th century.
Benito Mussolini seized power in Italy in 1922 and Adolf Hitler established a second fascist dictatorship in Germany in 1933. These regimes were characterized by a cult of personality, the suppression of dissent, and the use of violence to eliminate opposition.
Personalist dictatorships often last twice as long as military dictatorships but are more likely to end in violence and less likely to democratize. The death of the dictator often leads to the collapse of the regime due to the heavy reliance on repression to stay in power.
Most regimes exist in countries with high levels of poverty that destabilize government and cause regimes to fall more often. Economies based on natural resources allow dictators more power, as they can easily extract rents without strengthening or cooperating with other institutions.