The reason there is no clear answer is because there are multiple forms of pouchitis with different etiologies and disease courses. The most common one is related to bacteria, but it is not an infection. It is an inflammatory response to the presence of normal bacteria. This response is why pouchitis is relatively rare in those without IBD.
Other types of pouchitis include Crohn’s pouchitis, ischemic pouchitis (from poor blood supply), and infectious (like C. difficile and CTM infections).
There also is pouchitis-like syndromes, such as SIBO and irritable pouch. In these cases you have all the symptoms of pouchitis without the inflammation. You can also have dietary intolerances or cuffitis that can be confused with pouchitis.
Did you read the article posted in the “sticky” at the top of this forum? Lots of info there.