This observation is very interesting. I hope that it is studied more closely and we can read some peer reviewed research on the matter. One idea popped into my head: Could part of the cause be that people's mood and self-esteem improves during (GLP1 agonist-induced low hunger) weight loss? TL;DR: If you feel like shit about yourself (and body), then you are more likely to eat poorly, and vice versa.

That's an excellent hypothesis. Wouldn't be surprised at all if that was a component!