Answer:
Because when people are in turmoil - a bad situation - and a person who is (typically) charismatic and well-spoken tells you that they can fix everything, people will put their hope onto them and begin to let themselves get manipulated by the dictator.
An example of this are the dictators in WW2, who when their people were angry at the rest of the world and at their economic situations, promised great things and made themselves look like the common folk (to make the people feel a sort of relation to them), made the people feel even more patriotistic and fueled their anger even more.