Riding in a trailer can be harder on a chassis than racing it, particularly if it isn't properly supported or comes loose in the trailer. I have no idea how they support it or if it came loose, but a long ride can really do some damage.
On the track the chassis is quite flexible and is "suspended" on big Goodyears, so it has larger amplitude, lower frequency displacements with the tires helping the situation.
In the trailer it is usually tied down solid so the Goodyears can't absorb any vibration. If there is some flex, it would tend to be lower amplitude but much higher frequency, especially if the road is rough. Higher frequency = MANY more cycles, possibly many orders of magnitude more cycles than it would ever see on the track. If the vibration of the road drove the chassis to vibrate at its resonate frequency, the amplitude goes crazy and it would literally fall apart in short order. You've probably seen pictures of bridges swaying like crazy and ultimately shaking themselves apart when the wind drives them into a resonate frequencey....
My .02
