The midwest has lots of experience with powerful tornadoes, just look at how they handle them. Shelters, especially underground, are much more common. How to survive one is taught in schools, and very few don't know the drill.
The southeast has lots of storms, but few are as powerful and long-lasting as yesterday's. Shelters are rare, not many basements, and awareness of survival tactics is not well taught and heeded.
I grew up in the midwest, moved to FL at age 35. Locals just don't have the fear and respect needed to survive an F5.
And my observation ,in my area,is the newer any commercial building or home the less sturdy its construction.Large glass front,open floor plan ,flat roofed and on a concrete slab stores have NO real shelter capability.Nor can a home built to code minimums.And what many call a brick home is only a brick veneer that adds no strength to the structure.
The 1950s home shelter wasn't even that common then,much less now.The human response is usually to build back the same old way because of costs or other constraints,and besides "that will never happen again".
The miracle is that more weren't killed .
God please comfort the afflicted.