By impact, virulently. Crack is cocaine, so it was already illegal. And it was popular among the poor and brown in a way that powder cocaine never has been, but it doesn't have any physical or psychologically different properties. Smoking it is a more efficient delivery system than snorting it, by a little bit.
When a separate set of crack laws was enacted, the weight of the drug was given a 100:1 ratio. That is, possession of one gram of crack was the equivalent, for sentencing purposes, of possession of 100 grams of cocaine, a tenth of a kilo. Mandatory minimum sentences were enacted based on this. So a poor black person caught with 5 crack rocks gets five years, no exceptions, and a white banker with four ounces of powder coke doesn't get jail time.
This is a huge reason there are so many browns in the federal prison system.
Now, unlike MJ laws, there wasn't an explictly racist intention, but there was a dumb, unscientific moral panic that created laws that would clearly and obviously affect poorer, browner communities more than their richer, whiter counterparts.
And yes, some black leaders were behind such laws, far less so than the later VCCCA, Biden's infamous crime bill.