Modern vehicles are very strong, simply because they're designed to be. They are also good at absorbing impact energy throughout the whole body shell. This minimises the energy transferred to the occupants inside. So a modern vehicle looks like a complete mess after a hard impact, but it's designed to do that as energy is dissipated.
Something like a Defender or D1/2 has a sturdy chassis to keep the bumpers at the correct ends with all the other components bolted in the middle. However in a serious impact, that same chassis often deflects the impacted vehicle into softer non structural body shell components. This is one reason why the Defender was finally killed off, simply because it couldn't meet the stringent EU crash tests.
In light low speed crashes, the solid chassis vehicle normally suffers little more than cosmetic damage, whereas the modern vehicle is beyond economical repair.