Can editors review a manuscript and make a decision if they cannot find any reviewers?
The editor certainly has the power to reject an article without having it reviewed.  If they can't find a suitable reviewer, this is probably what would happen, unfortunately for you.

In some cases the editor might have the authority to accept it without an outside review, but this would depend on the policies of the specific journal.  Anyway, if they were planning to do this, they probably would have already done it.