As was said upthread, snow in the South often begins as sleet or heavy wet flakes. Then the temp drops and the slush freezes solid.
It can be dealt with but going TOO slow is as bad as going too fast. And being able to have some distance between cars helps. Of course, once traffic stalls, it’s all over.
We have lots of overpasses in our area of Texas and they do tend to get slick when the temps are below 40 and we have some moisture. It’s a real hoot to watch people drive over them. They go 70 mph until they come to the overpass, slam on their brakes, creep over the interchange area and then when at the end hit the gas and go barreling on down the road. Most drivers down here would never make it if we had real winter weather.