In 2006 Italians were already sick and tired of Berlusconi. The left-wing coalition were already planning a glorious victory, the problem is that it's a coalition formed basically by all politicians screwed by Berlusconi that inclusdes from catholics to communists, people who have in common little more than thair hatred for Berlusconi. Even before the election they were fighting for the best offices in the coming government scaring many people. Eventually they won anyway but they spent two years just bickering among them because they all had different agendas. The highest achievement of that left-wing government was trying to solve prisons overcrowding releasing thousands of petty criminals, too bad a lot of them got back in jail for new crimes within a few months.
After two years the left-wing coalition had to give up because they were incapable of governing and a new anticipated election was held. People were so disgusted that they voted Berlusconi again just because he's the devil you know!
Italy is still carrying the legacy of the Cold War, when vote was ideological, the country was a battleground for various terrorist groups and corruption was tollerated because there were worse things to think about. It's taking too long for Italy and particularly for Italian politicans to understand that today a lot of people can switch their votes to and fro the two coalitions and both of them seem to still showing how inadequate they are to govern a modern country.