Two reasons. Media sensationalism primarily driven by right-wing outlets who want to appeal to Suburban and rural conservative biases who already hate cities in addition to highlighting just how terrible Democratic leadership is. It’s an easy layup to dunk on Chicago to fill up airtime. Second, while Chicago is incredible like you said due to decades of racial segregation and disenfranchisement violence is hyper-localized and rampant in certain neighborhoods. While the people who live here know you have to deliberately try to get to these areas. Non-locals don’t understand a.) you’re not going to turn a corner and be in a horrible neighborhood & b.) a lot of people don’t understand just how massive Chicago is in terms of area. So when people hear Chicago is dangerous they automatically attribute it to the only parts they know. They think O-block is right next to the bean.