It helps to sway, or at least dissuade, people that aren't fans of, or even heard of, Cardi but were still considering voting for Biden. They see Owens call Cardi out for the vile person she is, see Cardi respond by being a vile person, and they think to themselves, "This is who Biden picked to interview him? He praised this woman? I don't want to be associated with this dumpster fire"
It helps to sway, or at least dissuade, people that aren't fans of, or even heard of, Cardi but were still considering voting for Biden. They see Owens call Cardi out for the vile person she is, see Cardi respond by being a vile person, and they think to themselves, "This is who Biden picked to interview him? He praised this woman? I don't want to be associated with this dumpster fire"