With Arrow, The Flash, DC's Legends of Tomorrow, Supergirl, iZombie, and Riverdale it's clear The CW doesn't think there's such a thing as comic book series fatigue. In particular they are ready to give Greg Berlanti and his "Arrowverse" as much latitude as possible, and that includes adding the Black Lightning series which he had previously set up at Fox.
Deadline reports that Fox has decided to pass on Black Lightning despite making a pretty sizable commitment to it previously. They made the decision after concluding the show wouldn't fit with their crowded genre slate. Remember they've already got Legion and Matt Nix's untitled X-Men show to go along with Lucifer and Gotham. Now discussions are underway for it to move to The CW, which obviously makes a ton of sense.
Berlanti developed the series along with Being Mary Jane creator creator Mara Brock Akil and her husband Salim Akil. Black Lightning centers on Jefferson Pierce, who had hung up his hung up his suit and retired from superheroics, only to be pulled back into action by a vengeance-seeking daughter and a notorious local gang who have their sights set on recruiting a star student.
A black superhero series on network TV is tremendously exciting. We haven't had one since...M.A.N.T.I.S in the mid-90s, maybe?