Because many of them are single issue voters. All you have to do is give them one excuse and they will vote for the same people despite the fact they are totally incompetent. The few Democrats that switched parties are long gone now. Their racism didn't go with them because it's still alive and well in the Democrat Party of today. It's just getting to the point the less and less of them can stomach voting for a Democrat anymore....thus the need for bringing millions of new voters into sanctuary states to prop up their voter base.