By selectively breeding forty generations of silver fox over the course of sixty years, researchers managed to make them as friendly as dogs

It's a domestication experiment, to study the genetic changes that occur in animals as they become more tame-- but the idea was to study those processes, not necessarily because the scientists believed they could truly domesticate an animal in the scant span of a human lifetime or even a few human lifespans.
The foxes themselves are not actually domesticated any more than any other strain of fur farm fox; the research was actually quite controversial among other zoologists and fur farmers alike, because they do some misrepresentation of their animals. Their findings-- floppy ears, curled tails, high white-marking... Are all already found in many other strains of farmed fox elsewhere in the world.
Whitemarks and Platinums both produce animals with just as much, if not more white found in the strains used in the experiment. They started with fur farmed foxes because they were already somewhat tame; so there is already question as to whether these genes were found in the backgrounds of the animals they started with, even if they didn't show on the phenotype of the fox itself.

Flopped ears and curly tails are just usually culled for in most bloodlines because they produce a pelt considered to be inferior quality (for most garment use, I don't think it matters, stoles that use full heads and tails haven't really been fashionable for decades). Some of their conclusions were picked up on by journalists, the public at large & even some other scientists for the -wrong reasons- & that has been a very frustrating part of the whole thing.

The research does have merit! Recording these changes formally (such as the minute brain size changes that are rarely mentioned in media coverage of the experiments) is important to understanding the processes that went into domesticating other animals and determining what events likely occurred first. It's just not as groundbreaking or new as some people have been led to believe. Encouraging people to breed foxes (and other animals bred for fur) for temperament and less stress in confinement is a good thing, even if it had already been happening for decades in much of the rest of Europe and the Americas before the Russian experiment even started.
Farmed mink are a very good example of this, anyone that thinks tame fur farm mink are spicy (and compared to a ferret, that is actually a domesticated animal that has been with humans for thousands of years, they are!) has not yet had the experience of trying to handle a truly wild one.

But there is a very broad misunderstanding with the public between domesticated & tamed (and to an extent, feral as well) that has not been adequately addressed by most of the journalists talking about this experiment.
Left to breed on their own, these changes would not wholly self-sustain the same way that they do in feral dog populations-- even the ones dangerous to humans!-- that have apart from humans for even hundreds of years, because dogs are domesticated animals with thousands of years and hundreds of thousands of generations behind them. Even dingoes retain traces of their domesticated past in terms of changes to areas of their brain, and they have been (mostly) outside of human control for thousands, not merely hundreds of years. :P

Tangentially, that broad misapprehension of the difference also leads to annoyances like people trying to fight for the "rights of wild mustangs"... That are simply feral populations that we abandoned in the first place, damage the environments they aren't native to, and do better in human care. They tame down quickly and become trustworthy because they were not actually wild. No matter how much time you spend working with a truly wild equine species, you aren't going to come away with an animal that is behaviorally close to one of those "mustangs". There have been a few people that have done some truly impressive work with zebras or other wild asses, but they are very aware these animals are very much the exceptions in the hands of very talented (and sometimes equally questionably moral) trainers and not examples of the baseline of their species.