You seem determined to believe that the rejection was for "political" reasons despite having no evidence for this claim. The quoted reasoning was not "lack of fit" or "lack of interest," it was lack of "interaction with other areas of mathematics." Going back to my first comment, there's a general sense in the community that this sort of interaction among mathematical subfields (or with physics) is prized in research, and it's one of a few criteria that form the sociologically dominant view of what constitutes "good mathematics." You might disagree with these criteria, but it's not hard to see why that paper might lose out to other excellent papers when judged by them. This doesn't look like politics (favoring "insiders") to me; it looks like the consistent application of a value judgment about what good research is.

Again, whether you think the criteria should be the way they are is a separate conversation.