What are the factors that have contributed to the rise of the Movimento Cinque Stelle in Italy? Why has it gained popularity?
tl;dr I think its success relies heavily on anti-establishment message (e.g. unwillingness to form political alliances) and the modern approach to politics (e.g. e-democracy, direct democracy) that catch young votes' attention.
Modern democratic tools - the party promotes modern ways of voting (i.e. electronic voting, more direct democratic methods)
The Five Star Movement, in order to go in this direction, chose its Italian and European parliamentary candidates through online voting by registered members of Beppe Grillo's Blog.
The choice to support the abolition of a law against immigrants was taken online by members of the M5S even if the final decision was against the opinion of Grillo and Casaleggio. The partnership with the UK Independence Party was also decided by online voting.
No "old" politicians - the party tries to apply a maximum number of mandates at any political level, thus ensuring "fresh faces":
no one who has already been elected twice at any level (local or national) can be a candidate again and has to go back to his or her original job Another feature of the movement is the so-called "zero-cost politics", according to which politics must not become a career and way to make money.
Integrity rules - the party does not allow members with criminal record:
The party also supports initiatives to ban politicians with criminal records from being elected. Among the greater political battles of M5S is the ethical commitment to a greater simplicity and transparency to counter the practice of holding two or more positions
Tolerance towards sexual minorities:
The leader of the movement, Grillo, on 15 July 2012 publicly expressed his support for same-sex marriage
Ambiguous position on immigration and European integration - avoid a clear position on such sensitive topics might not divert some voters
Filling an electoral gap - some argue that the young voters (<34) are not represented in Italy and this party fills that gap:
Almost all the young people I spoke with felt that the traditional parties spoke mostly to older voters, and failed to offer concrete plans to help young Italians find employment. There is electoral strategy at work here: Voters aged 18 to 24 make up just 7 percent of the total population of Italy; those aged 25 to 34 make up just 11 percent of the population, Ipsos pollster Mattia Forni told me. “Maybe … for this reason, youth issues are completely, or nearly, missing in the political campaign,”
The party not only that has clear message towards the young, but also promotes young people within its leaders:
The party has pledged to introduce a universal basic income for all Italians, cut down on short-term work contracts, and invest an additional 2 billion euros in the labor market. What’s more, the party’s lead candidate is the 31-year-old Luigi di Maio, who in 2013 became the youngest-ever vice president of Italy’s lower house of parliament, the chamber of deputies.