If you look at people’s body types, one can see that some people are thin by nature and some fat by nature. The thin ones have as much difficulty putting on weight as the fat ones do losing weight.
I am happy for your success - if you are happy! :-)
Just because this topic interests me, do you mind if I ask how you lost the weight and what you do to maintain it? Do you know how many calories you consume on a daily basis? How about exercise? You are, of course, in the minority. Most people cannot maintain weight loss for any significant amount of time.
We'll have to agree to disagree on that people cannot maintain weight loss for long. Of course they can. They just won't because will power and consistency is difficult and a constant struggle. If they kept up the same eating and exercise habits as they did to lose, they will keep it off. I ain't saying it's easy but it's certainly doable.