I rejected a manuscript yesterday when reviewing for a peer-reviewed journal. The main reason was that the authors did not tell me why they conducted the study at the end of the Introduction.
The authors stated that they performed a study because it was the first on a given topic. As a reviewer, I have no way to verify this claim, and being the first ever pioneering study, if true, should not be the reason for conducting any study or having the study published. I do not see the importance of being the first. What is important is why no one has done the study, why you wanted to do it, and how you did it. The study has never been done because 1) no one found it interesting, 2) no one asked the research question, 3) no one had the means to answer the research question by conducting a study, or 4) you've found a new angle to answer an old question. If you can elaborate on any of these reasons, then being the first will be an very interesting fact of the study but not indicative of the quality of the study.
Here is my suggestion regarding how to make the case why you conducted a study when writing a manuscript about it -- Work backward and then forward and back again when writing the Introduction.
You've done the study. You have results and just started writing it up. This means you have performed analyses to answer your questions no matter the analyses are hypothesis-driven or data-driven. At this point, you write down the research question before the header Methods. That is, the research question concludes the Introduction section. Perhaps you may write the question in the form of an objective, such as: The present study is to determine whether A mediates the effect of B on C. Then you write this very last paragraph of the Introduction section by thinking back why you conducted the study in the first place, months or even years ago. Once this paragraph is drafted, you jump back to the beginning where the header Introduction is located, and write the first paragraph of the Introduction which usually is the background of the subject matter.
Now you have the beginning and the end paragraphs of the Introduction. In other words, you've got the top and bottom of the inverted pyramid -- broad research area and targeted research question, which give you the framework of the content in-between that you have not written yet. I suggest you now leave the Introduction alone and get back to write up the Methods section, which should clear your thoughts through the process of describing concrete study procedures.
When returning to writing the Introduction, you have recalled and documented all the research activities you've done. You should have a relatively clear idea how to connect the first and last paragraphs. You write the second, third, and maybe fourth paragraphs focused on more and more detailed literature review that specifically relevant to your research questions until you connect the first to the last paragraph, which you wrote first. The transition may not be smooth yet but should be apparent. This is where the "back again" occurs. You read what you wrote in the last paragraph and may revise it to make it fit better with all the previous paragraphs. Then you should be able to find a good transition and create the flow, leading the readers through a logical narrative to the reason why the present study was conducted.
Then I will be very happy to review it.
