Yup, that's kind of how metabolism works. If you run a caloric deficit, you will lose weight...
In the same way that some people drink massive amounts of alcohol in college and turn into alcoholics ruining their lives and liver, and others just 'phase' into a more healthy lifestyle, clearly some people find it harder to do what you did than you.
One conclusion is that they just don't try hard enough, and they're not as 'good' as those who do. They willingly choose to live a lesser life. Because they're lazy or whatever.
The other, more complicated (and I'd argue less arrogant and more empathic) conclusion is that the psychology of addiction is different for different people, and approaches that work for one person don't work for others. And rather than saying 'it's really that simple', we should research the problem and devise solutions that take into account the simple fact that some people apparently drink until their liver gives up and all that's good in their life is eventually gone, or that some people apparently eat and grow fat and hate themselves and live 'lesser' lives instead of getting in shape.
Having spent a lot of time with 'highly successful and driven' people, and having spent a lot of time with fuck-ups who suffered from a variety of addictions, I've come to the conclusion that being that hard to define 'good' has little to do with it. Instead, it seems that the difference is mostly upbringing and environment (where this environment was usually not a choice, but rather a circumstance).
I've been lucky to be surrounded by both happy, successful people and major 'fuck-ups', and as a result my life currently occupies a mostly happy space. But I have no illusions that this is primarily the result of my personal choices and willpower, as willpower itself is a result of upbringing and environment.
Sure, my will and choices matter. I don't want to remove personal agency entirely. But even if my current (happy) state of being is 50% a result of factors outside of myself, it's enough to realize that I'm fucking lucky, and those who fare worse than me need support and researched solutions rather than 'it worked for me, so it should work for you'.
If it takes even more than what I tried then I hardly believe it's even worth it. I'd rather live happily for one less year than never get to eat fulfillingly and live on a bootcamp exercise regimen.
One of the main problems people have with counting calories is accurately being able to do so. While I don't think counting calories is for everyone, if you do try again, try to weight everything you eat. Don't forget the teaspoon of olive oil in the salad and those kinds of small things that add up. Research has shown that comparing food logs of people that say they have a slow metabolism and that they count calories, when subjected to something I think is called, reverse isotope water (or similar), shows that they are not accounting for a lot of the things they eat.
Also, a month isn't a long time to notice changes even on the scale. It isn't uncommon to not drop weight due to water retention during a few weeks (depending where you start) when starting a diet.
Apparently my BMI is 'obese' but I don't feel or look 'obese', by whatever value of obese seems to be my intuition gained over time, oddly. Maybe overweight is so common that it looks normal.
BMI is not really accurate on the individual level. Most athletes will score on the 'overweight' range for example while athletes that play in weight division sports will be in the 'underweight' category a lot of the time (I was for example, but I doubt anyone would consider me underweight at the time).
You also don't have to live a bootcamp experience, since essentially all your weightloss will come from not eating too much. Calories are flexible though, if you note which foods you get most saity/calorie then it is better to go with those foods than others that may be "healthier". In my case the key turned out to be meat and higher fat content plus bread.
Your month may have sucked, but you can absolutely do it, you will live better for it and whether you die earlier or not your quality of life is going to be much, much better when you aren't fat. It isn't just a matter of dying earlier - that tradeof may seem worthwhile - but a matter of whether you will spend ten years in a wheel chair, whether you can reach your own butt to wipe yourself, whether you need a machine to make sure you don't die in your sleep, etc.
You can totally do this. I know because I have been down that route and yes, the payof is worth it. Email me.
The water/muscle sound like reasonable explanations.
My overweight relatives had reasonable mobility etc into their 80s while still being overweight, so maybe my genetics are fine for it, but being healthier might be a net positive as you say anyway. I'll consider it.
Obesity appears to be highly heritable. For this reason a careful balance must be struck between encouraging people to control their weight and not blaming them for have been dealt worse cards than their naturally slim neighbors (until we have a cure).