it originated way earlier as a way to help people who have naturally small nasal passages. i guess both mewing and chewing help widen passages. The book breath goes into details but from the perspective of health and not looks. This has been known for like 100 years but mostly dentists payed attention to it.
The fact is mewing and chewing do make a measurable difference…over time. Tiktok promotes extremes as they get more views and the more extreme the more views in a cycle of escalation. This gave birth to sad boys who see the Toyota chivalre’s and think they need the same jawline. Similar sad nonsense has been going on for women too but that has unfortunately become all but normalized.