It may not be obvious that the size of the trains are causing derailments, or at least not to the "Wall Street People". Your comment assumes that everyone has perfect information and asses the available information in an unbiased purely rational way, but in reality that's often not the case.
(No opinion if this actually is the cause, or what the dynamics are here; I don't know anything about trains or the businesses surrounding them.)
(No opinion if this actually is the cause, or what the dynamics are here; I don't know anything about trains or the businesses surrounding them.)