As a relatively newfangled academic editor of PeerJ Computer Science, I can tell you that actually finding suitable reviewers is substantially more difficult than what I used to give it credit for. For many papers that I get on my virtual desk I am not actually an expert, so I need to invest some time to look over the literature of the area to figure out who actually are suitable reviewers. My current "acceptance rate" for reviews is substantially below 20%, and it would be even much lower if I did not have a reasonable personal network (that is to say, at least 75% of all reviewers that actually accept are people I know personally). Approximately 50% of those that do not accept never respond, so you can't really tell whether they accept or not until you waited a week or so. And - particularly annoyingly - it is not unheard of that people accept a review but then never get back to you.
All in all, I would say taking one month to find reviewers is long, but not outrageous.
I believe the effort required to review a manuscript is much greater than the effort to find a reviewer.
While this is certainly true, an editor also typically handles many more manuscripts than a reviewer...