Not sure, but discussions regaring crohn's disease clearly went completely off track after the 1970s. During the 90s and 2000s, crohn's disease was referred to by GI as an "overreactive immune system" without any proof. GI were adamant that dietary manipulation was useless.
Pathogens didn't matter, regardless of the fact the intestine is exposed to the highest number of bacteria and fungi, crohn's disease was simply "autoimmunity" where our immune system decided to attack our own intestine one day for some reason, no proof of a self-antigen was even required to spout this nonsense.
Only now are we seeing some sense return. EN is again recommended, not only for children, but also adults.
Now we are finally seeing some sense coming back, and papers that show innate immunodeficiencies in crohn's disease manifesting itself as early phagocyte incompetence (macrophage and xenophagy incompetence, ATG16L1), lack of pathogen recognition (NOD2), lack of neutrophil recruitment being referenced again, and the realisation the fecal stream high in bacterial load is involved in inflammation.
Crohn's disease and UC are talked about as independent diseases again. Not just "IBD" which is a horrible term. The fact treatment needs to be disease and location specific, the fact Crohn's disease and UC involve very different genetic anomalies. The realisation that the ileum is very different from the colon and will respond very differently to treatment.
Note that GI from the 70s all knew this already. Note they realized crohn's disease involved immunodeficiency, and the realisation that reversal of immunodeficiency towards immunocompetence is required to see resolve of disease state:
"....nonreactivity to DNCB, and also in their failure to respond to the mitogen PHA.... there is a body of literature that supports the notion that there is a return to immune competence with intravenous hyperalimentation. ..."
