I really thought the old one would have done better than the new. I though the full frame would hold pretty solid.
The frame probably does hold pretty solid. However, since it's a body-on-frame car and the body is bolted to the frame and it's the body that takes the energy, the strength of the frame is irrelevant to passenger survivability.
to crumple zones
Crumple zones, better passenger compartment rigidity (notice the A-pillar on the Malibu doesn't bend at all, whereas the '59 pillars distort enough for the windsheild to come out whole) and better passenger protection inside the vehicle (three-point seatbelts, airbags, collapsible wheel/column, padded surfaces without sharp edges) all contribute to vastly improved survivability in modern vehicles versus their older counterparts.