Is it fair to reject manuscript with few words of comments after long 9 months of review?
I can't say about fairness, since the manuscript might be indeed of limited interest. On the other hand, I would have contacted the editor after two months under review.
It's possible that the manuscript had been forgotten either by the reviewers or by the editor.
But what seems to be quite probable in this case is that the editor might have been searching for reviewers, but none showed interest or kept giving up in the process. That would explain why there was no reviews attached to the answer (which is usually the case when the editor decides without reviewers feedback).