To be fair, a lot of people outside the US don’t know anything about Halo either.
It makes sense one wouldn’t know about Free Fire if they are not privately or professionally invested in SEA and LATAM markets, or mobile gaming as a whole. Just like I am perpetually perplexed by the existence of Israeli juggernaut Coin Master.

Grrr, that stupid pig forever mocking me!
Free Fire should be around $400M revenue for 2022, for reference. The game used to be a perennial Top 10 attendee but the emergence of PUBG Mobile and recently COD Mobile, in addition to the ever ongoing upgrade of “lower end” smartphones, have dented its popularity in the past couple of years.
A similar phenomenon specific to China and even moreso Japan is NetEase’s Knives Out, known as 荒野行動 (Kōya Kōdō, wild behavior) locally. Knives Out was basically Free Fire’s main rival as the other extremely fast PUBG copycat on the smartphone market circa 2017, back when PUBG exploded on PC. Specifically for Japan, the one year exclusivity deal for PUBG on Xbox One and (back then) low market penetration of gaming PC made smartphones the perfect destination for a local boom of battle royale games, especially among teenagers. Both Knives Out and Free Fire eventually got sued by PUBG’s owner Krafton.
If you are interested in the wider topic of under?discussed gaming juggernauts, the Insert Credit forums had a good (if short) thread on this phenomenon in 2021 and Free Fire was mentioned back then too.