CFS is far from neglected and there have been a number of studies attempting to show a physical cause. We've had a number of false positives that have later been debunked.
> the most successful treatment programs tend to focus on careful regulating exercise and diet which again seems to be largely physical.
This is coming from the PACE study, I'm assuming. PACE is largely viewed as suggesting that CFS has a substantial psychological component. There is a bunch of other literature on this as well.
Exercise and diet changes are usually successful treatments for psychosomatic-like illnesses, so I disagree that this treatment means that it is a physical disease.
Many of the original researchers who provided evidence that the disease is non-physical in nature have since left the field after extensive death threats and harassment. [0]
> Reuters contacted a dozen professors, doctors and researchers with experience of analysing or testing potential treatments for chronic fatigue syndrome. All said they had been the target of online harassment because activists objected to their findings. Only two had definite plans to continue researching treatments.
[0]: https://www.reuters.com/investigates/special-report/science-...