According to other comments it was a match against Bremen, who have left wing ultras, and Leverkusen ultras have apparently been trying to pick fights with them to become relevant

Some clubs in Serie B could be higher like Palermo or Sampdoria or Bari but a lot of people don’t bother going to the stadium it it’s not Serie A or a promotion playoff, it’s kinda sad because half of them support juve/inter/milan instead of their local club