https://operations.nfl.com/gameday/analytics/stats-articles/where-have-all-the-points-gone/
That does seem a valid question.
https://www.teamrankings.com/nfl/stat/points-per-game
Although there is evidence that it may not have been just a one-off event last season, there are a couple of things which may have contributed to both cause and attention. One is the pathetic fact that 4 teams including Our Heroes, Jets, Pats, and Panthers set a new standard for futility in scoring, and that this year's champion Chiefs tied for 15th in scoring average, a full touchdown, 7 points a game less than the year before.
While adjustments in Defensive strategy and tactics no doubt have been a factor in the reduced scoring, by no means has it been the only one.
Cheers!