I'm not saying he had to run an ad for every crime. Here's how it went: Donald trump was part of this large movement of racist rhetoric against black people. He went around saying young blacks were roaming around the city doing "wildings" like animals, just preying on specifically white people to beat and kill them for fun. This was baseless, factless rehtoric that was purely fear mongering and making people play into the idea that blacks are dangerous and lesser. There were many heinous crimes around that time, but trump didn't care because it didn't play into this narrative of the evil pack of wild blacks roaming the street for sport. Then there was a case that fit his narrative so he whipped out outrage about it (focus here: they were a group of black kids attacking a white woman, that dope fact is the reason trump got "outraged" about it, that's the sole reason he picked this case in particular). He then called for the death penalty, a punishment not used (and still to this day not used) since the 60's in New York, in a case that was not even close to being the most heinous crime that occurred during that time. He chose this case because it it his baseless, racist narrative and then pushed to have these kids executed.

It's also stupid to point to their conviction because they were clearly innocent. The police, because they were young black teens, didn't not give them any of the rights theye ere entitled to, did not contact or have their parents present even though they were minors; forced confessions out of them and used that to push conviction (even though the confessions didn't match each other or the evidence found at the scene). The prosecution knew the evidence pointed to their exoneration yet ignored it. It was an incredible miscarriage of justice and mostly pushed politically because of the major racist rhetoric that was whipped up by people like trump. You can expect similar situations to arise in the future if trump becomes president and keeps up this fear mongering against immigrants and refugees.