I read the article and the abstract, unfortunately have not located the full study, but it seems rather low quality evidence to be making such correlative statements. The biggest question I have about how they came to their conclusions is: Was there any assessment of their religious fundamentalism prior to their TBI? It sure would be nice to have that assessed in order to determine stronger correlation to the TBI impacting their level of fundamentalism. If they were fundamentalists before TBI, I could easily see the experience of TBI (and their survival of such) as only further encouraging such fundamentalist belief (most fundamentalists would easily credit God's intervention in their survival and recovery, thus providing a positive feedback loop to their already clung to beliefs). If the converse were true and they were less or not at all fundamentalist prior to TBI, that would certainly impact their findings as well. Certainly a fascinating area of study, but far more research is needed to make any relevant statements.

And here I thought it was because their medulla oblongata was enlarged

It is not clear to me from the article what caused the alleged damage. What appears to actually be the case is that certain kinds of damage are consistent with promoting fundamentalism but even they admit that it's 80% other effects that influence fundamentalism. So unless I'm completely misunderstanding something, this article doesn't say all fundamentalists are brain damaged or that all fundamentalism reflects brain damage. I think the headline is designed to attract eyeballs but the article itself simply establishes a potential association (among many), not a cause.

Or to take advantage of an already-overused phrase, "it's a nothing-burger".

The gullible would not do the exercises. They have a great need to know what we cannot know and only through bible belief do they know this. As a religious woman once asked Bill Maher "let's say that you were hungry." Bill stopped it by declaring he was not hungry.