Some answers are not found because the right questions aren't asked, not even in " the largest longitudinal study of its kind in the world" -- and that study will be no different. Certain assumptions were made when that study was being set up, and so the "answers" found will be limited by the constraints in practice devolving from those assumptions -- you just have to found out in what ways they are.
Similarly, ask yourself with respect to that study, what's so significant about it -- what are the real world implications of what was "found" and what was "said to be found" -- not always the same things. And in sociocultural terms -- what are the real world implications of the settings in which people try to implement what they see needs to be done. If in the US, the implications, for children, will be in terms of diagnoses -- and not all professionals' "diagnoses" will be accepted as grounds for IEPs; similarly for other types of "solutions" / treatments people may wish to see applied. In New Zealand, principally (solely?) diagnoses made by psychiatrists will be accepted as justifications for certain interventions. Academically, in New Zealand, especially in southern New Zealand as far as I know, there's a dearth of clinicians in universities able to promote biopsychosocial formulations to clinicians in training, with a resulting bias towards bio-bio-biological formulations -- the situation being quite different in England, with the British Psychological Society in particular, being much more prominent in "socially acceptable" diagnostic formulations. In the United States, one needs to only think briefly about the tortuous history of the diagnosis of Developmental Trauma Disorder to see the truth of the proposal that one needs to consider the sociocultural heritage of clinical researchers in understanding and comparing their contributions. Sometimes one can only become aware of these "biases" until one receives other articles (personal communications!) from the clinical researchers involved -- a good reason to not just accept single papers on face value. An example of the latter is relevant to "understanding" your quote of Danese et al -- which on the surface one would think says that the social environment in which childhood trauma occurs does not play a role in the affected child's suffering cognitive impairment. Yet in a paper written at about the same time "The hidden wounds of childhood trauma", by Andrea Danese & Anne-Laura van Harmelen, which says "Supporting the role of inflammation in mediating the association between childhood trauma and later disease, experimental research in rodents showed that administration of anti-inflammatory medications can buffer cognitive impairment after early life stress (Brenhouse & Andersen, 2011). However, more research is needed to directly test mediation processes in humans (Danese,2014). " (p. 2), so Danese' position might not be as clearcut as your quote suggests ?