"Star Trek: Discovery," premiering later this month, has chosen to focus on the first officer, noting that this is different from the previous series' focus on the captains. The odd decision is not the rank of the character, but the fact that they are focusing on only one character at all. The previous series did not focus solely on the captain, but several members of the senior staff.
Star Trek through the years
The focus on other characters is as old as the series itself, leading actor Leonard Nimoy to write a book titled "I Am Not Spock" and 20 years later, "I Am Spock." Further, one of the often-stated references to the original show, "Beam me up, Scotty." features the name of another senior staff member.
This is commonly thought to be a line by the captain of the series, James T. Kirk, but this line is never said in the original series.
"Star Trek: The Next Generation" has several arcs, but all of them focus heavily on several of the characters. The captain, Jean-Luc Picard, has his most dramatic moment in the episodes "Best of Both Worlds." Before I go on, I will say that the following sentence or so will contain spoilers for a show that ended production 23 years ago; if you haven't watched it by now, you may want to skip ahead. In this episode, the captain is assimilated by the Borg, a species known for taking other species' individuals and technology to incorporate them into their collective.
Using Picard, the Borg attempt to attack Earth, but this episode, instead of focusing on our captain being stripped of his humanity, looks at his first officer and (of all the crew members) the bartender. This episode features a scene that helps to flesh out the relationship both of the characters have with their captain. The scene culminates with the first officer, Commander William Riker, accepting the fact that he must fire on the ship containing his captain and friend in an attempt to kill him and destroy the ship.
As the captain is going through an event so traumatic that it will be referenced in several later movies and series, the show chooses to focus on Riker, as he must make one of the hardest decisions of his career.
When does the show take place?
If you were skipping past the spoilers, you can start reading again. Taking place after the events in "Best of Both Worlds," we see what is perhaps the most polarizing of the many incarnations of the franchise, "Star Trek: Deep Space Nine." The major plots of the series focus on Jadzia Dax, Odo, and Kira Nerys, only one of whom is even a member of Starfleet.
The three characters have vastly different storylines that stand alone from or complement the story of the captain, Benjamin Sisko.
This new series has made a choice to focus on one character, and that is what makes this strange, not who that character is.