Fair questions, and IMO, it's a combination of source of fault- the medical profession, big pharma and big food. Processed food is a huge contributor to obesity. The foods are chemically formulated so that many people will overeat and become obese. There's one jackass who I have on ignore who says it's the individual's fault for getting obese. But IMO (and a lot of others), it's not that simple. Similar to alcohol and drugs, some can not consume drugs/alcohol at all, and some can drink in moderation without developing a problem. Same thing for processed food.
In years of going to family doctors, not one gave concrete and useful advice on how to eat to maintain or lose weight. The media (magazines, newspapers, TV, social media) puts out a lot of misinformation. Government agencies and major universities are funded by big Food companies, and they have no incentive to promote healthy eating.
There are functional medicine doctors (a rare bunch) who promote healthy eating and lifestyle through a focus on eating the proper amount of protein (about 1 g of protein per pound of body weight) and a reasonable amount of healthy vegetables, while minimizing (preferably eliminating) highly processed foods (pastas, breads, chips, etc) and sugar-laden garbage "food". This is 80% of the battle. Add in a moderate amount of exercise, and obesity is not an issue. Sounds easy in principle, but finding that answer and adhering to this is not simple for most people because the quick and easy foods are often the least healthy.
So the medical profession throws ups their hands, and start writing scripts for things like Ozempic when the side effects and long term issues of taking these drugs are unknown. The system is broken, and big food and big pharma have no incentive to fix it.