You'd also want to know recurring rates, 30-day unique numbers, and stuff like that... but even aside from all that...
Traditionally media product consumption is very age-stratified, with people time constraints and choices changing with phases of life.
Even historically pre-games, this would apply to the types of shows or movies, so the most popular teen show in the world may not dominate office chit-chat the same way the most popular-among-adults entertainment would, say Monday Night Football.
Now there are way more forms in play then there used to be. Fortnite is very new. Gaming participation among my age group (millennial) certain has changed with aging, as many of my former die-hard gamer friends no longer devote nearly as much attention to it, but have picked up "old person" habits like passively watching HGTV while doing household chores instead. Similarly, even now when I'm working with very gamer-heavy coworkers... it's not Fortnite.
So it's entirely possible for something to dominate in revenue and overall any-single-instance participation numbers yet be less relevant to the "mainstream" mid-20s-to-middle-aged conversation... It's also possible for that conversation to continue to fracture.