NBC’s lineup underwent a bloodbath ahead of welcoming back the NBA this fall, when “Found,” “Suits: LA,” “The Irrational,” “Night Court” and “Lopez vs Lopez” were all canceled. While fans of the series lamented the cancellations, a closer look at the ratings explains why freshman shows “Brilliant Minds” and “The Hunting Party” joined the ranks of renewed series while others didn’t make the cut.

NBC’s three “Chicago” series, all of which scored renewals, were the network’s most-watched shows of the season, according to multiplatform live-plus-35-day viewing figures, with “Chicago Fire” averaging 10.36 million viewers, and “Chicago P.D.” and “Chicago Med” at 10.05 million and 9.59 million, respectively. Like past years, the “Chicagos” and two “Law & Order” shows were consistent hits, with “Law & Order: Svu” and the original “Law & Order” bringing in 8.92 million and 6.76 million average viewers.

Notably, “Brilliant Minds” and “The Hunting Party” — the only...