Batman may have locked up The Riddler in The Batman, but The Penguin sets phase 2 of his plan in motion. DC‘s The Penguin opens with Gotham still reeling from the Riddler’s actions. The flood caused extreme damage to Gotham’s infrastructure, especially in lower-class areas. Many people lost family and loved ones, including Victor Aguilar, whose family died in the flood. Riddler may be stuck in Arkham Asylum, but his violent message still affects Gotham. Many citizens want to fight back against Gotham’s corrupt institutions, and Riddler’s message remains alive even when he’s gone.

https://screenrant.com/the-penguin-part-2-riddler-plan-expansion-explainer/