I believe the reason tvN is pushing forward is because they think it will be profitable.

Considering Cho Jin-woong's role in "Signal," having a vicious criminal preach about justice is truly nauseating and a factor that breaks immersion.
However, there are people in Korea who do not care about what kind of person an actor is, and people overseas will care even less.
Furthermore, if the quality were low, they might have abandoned it, but looking at it internally, I think the production quality seems decent.
Therefore, I believe tvN is pushing ahead with this because they think it will make money, even if they face criticism.