The idea that ME/CFS is due to some "hit and run" damage in the brain resulting from an acute viral infection has been around a long time, and is an interesting idea.
However, one argument against this hit and run theory is the fact that improvements and remissions from ME/CFS that can be obtained from virus- or immune-targeted treatments such as interferon, oxymatrine, low-dose naltrexone, IVIG, Valcyte or Valtrex, and of course autoimmune-targeted therapies like rituximab. If ME/CFS were mainly due brain damage, you would not expect antiviral treatments or autoimmune therapies to help.
Although I take your point and suggestion that infections, inflammation and autoimmunity may be involved in addition to the brain damage, and that the therapies help by addressing the infection, inflammation or autoimmunity side, but not the brain damage side of the illness.
In fact my own ME/CFS appeared not that long after an unpleasant episode of viral meningitis and/or encephalitis (I am not sure which, you can also have both together as meningoencephalitis). During this brain infection, it felt as if someone was going through my brain and surgically cauterizing or removing various connections and functional areas, as immediately after the episode (which only seemed to last an hour), several aspects of my personality and mental faculties were irrevocably altered or destroyed. So there seemed to be definite and permanent brain damage from this brain infection, and in fact I have never been the same person since.
Some of my lost faculties restored themselves within a few months (for example, I lost the ability to recognize faces after my brain infection, except for very familiar faces like my immediate family; but fortunately this faculty slowly returned after some months).
However, my ME/CFS did not appear in its full aspect until around at least a year after this brain infection. So in my case there was no clear connection between my brain infection and the onset of my ME/CFS, although I guess the brain damage it caused may have played a role in my gradual onset into ME/CFS.
Or another possibility is that my acute meningitis/encephalitis resulted in the virus initially entering the brain (and causing some damage), and then once in the brain, this virus over the coming months slowly infected more areas of the brain, leading to ME/CFS. Enteroviruses can produce fierce acute infections like my initial brain infection; but they can also cause slow, low level, chronic smoldering infections that linger in the tissues indefinitely (non-cytolytic infections).
One study on those who suffered an episode of viral meningitis found there was a higher prevalence (12.6%) of ME/CFS after meningitis compared to the prevalence in the general population (0.2%). So it does seem like a viral infection in or around the brain can be a risk factor for developing ME/CFS (although one has to be careful with such studies, because viral and bacterial meningitis was found to cause pituitary dysfunction leading to growth hormone deficiency in 29% of cases, and growth hormone deficiency can closely mimic the symptoms of ME/CFS; so you may think you developed ME/CFS after meningitis, but in fact it may be growth hormone deficiency, which is treatable).
In general though, meningitis and encephalitis do not seem to be common precursors to ME/CFS, and this also tends to argue against the hit and run brain damage theory as a major cause of ME/CFS: because if the hit and run theory were generally true, then you might expect that most ME/CFS patients would report a meningitis or encephalitis brain infection prior to the first appearance of their illness, which they don't. I've only come across one or two other ME/CFS patients on this forum who experienced meningitis or encephalitis.