Thousands of people from the "movimento delle Sardine" ("Sardines movement") are singing Bella Ciao as a protest against some right-wing political parties.
The Sardines movement is against populism, fascism, racial discrimination, and sovereigntism.
Sardines are against anti-euro and anti-EU parties: that's why there are European Union flags.

More information about the Sardines movement: https://en.wikipedia.org/wiki/Sardine...
Some photos about the event in the video: https://www.ilpost.it/2019/12/11/sard...

TIMESTAMPS
0:00 Bella Ciao
0:10 Humming
1:05 Singing softly
1:55 Singing normally
2:40 Grand Finale
3:15 End