I agree that the revolutions that occurred in the years 1820-49 were due to a lack of popular support. Other factors could be the strength of the Austria army, how there was no leader, a lack of unity and no foreign support.
The revolutions failed due to the lack of popular/mass support. The revolutions in Modena, Parma and the Papal States had all been unsuccessful as The peasants that made up the majority of the population were generally not interested in unification. This is not surprising, since unification would not have had any tangible benefits for them. They were more interested in their immediate economic conditions; whether they had enough food. The peasants could only be used to help bring about unification when they rioted due to economic depressions and food shortages. The main supporters of Italian unification were, instead, the middle and upper classes therefore possibly the reason why the revolutions failed was due to the lack of support
Another reason for Italian Unification failure was the influence of Austria over Italian provinces. Austria had very strong domination over Italy. It had agreements with Ferdinand, king of Kingdom of the 2 Sicilies, and helped the pope maintain his kingdom. Only Piedmont Sardinia wasn't influenced by Austria. The rulers of Parma, Modena and Tuscany were directly or indirectly related with the House of Hapsburg. The ruler of Naples had concluded a treaty with Austria. The Pope of Rome was the supporter of Austrian policy. In this way, Austria was the real master of Italy. They helped to destroy the success such as in Modena and Parma where their leaders fled for safety. However, the Austrian army always, quickly defeated the revolutionaries causing the revolutions to fail.
One other reason for revolutionary failure was the lack of a true leader. Although various leaders of Italian