I've looked up the source of the oft quoted "fact," "95% of diets fail."

Not only I, but others have searched for it, and nobody can find it. If instead of searching for "why diets don't work" you look for "why do some people succeed in losing weight?" you'll find at least 20-30% of people who try to lose weight succeed, and keep it off for several years or more.

We want to look for explanations - it's genetic (this has been thoroughly debunked); it's due to increase in anti depressants (may be true for 5% of the overweight population), chemicals in the environment (possibly for 1%), excess carbs (as you say, as many people fail on keto as on other diets) or an increase in low fat diets (given that on average, 1-2% of people on diets choose low fat, and this has been consistent since the 1980s, the only way one could support this idea is to assume that somehow by osmosis, 98% of dieters who fail to lose weight are somehow influenced by the small proportion of people on low fat diets!!)

As a psychologist whose main job is fostering behavior change, I think it would be nice just to admit what humanity has known for, well, 250,000 years: Habit change is hard. We live mostly in our desires and fears, few of us have remotely well developed pre frontal cortexes, which are the uniquely human parts of our brain responsible for making choices.

In fact, one of the single most powerful means to support habit change is to acknowledge its difficulty. Our expectations then are modest, and we can succeed!

Meanwhile, congratulations on your weight loss!