If the .41 failed then they wouldn't have continued to make ammo or chamber guns for it. Just because something isn't as popular as something else doesn't mean it failed. It failed in its target market (law enforcement), but plenty of sportsmen, collectors, and self defense shooters kept it alive, just like the 10mm was kept alive for nearly 30 years before it started gaining popularity. .41 Mag will always be a niche cartridge, but it's hardly a complete failure.
You obviously don't know many Ten Mil guys. The .40 S&W was based on the 10mm. In the early 90s the FBI adopted the 10mm Auto to replace their .38s and 9mms after a disastrous shootout with a couple of guys in Miami (1988 I think?) where each of the bad guys took literally dozens of rounds of 9mm, .38, and even buckshot before they stopped shooting back. The FBI decided they needed to issue their agents with a more effective pistol/cartridge combo and with with the Smith and Wesson 1076 (used to own one that was a former FBI sidearm and I wish I still had it) in 10mm Auto. It was a big, single stack auto nearly the size of a 1911. The HRT even started using H&K MP5s chambered in 10mm. The problem was most FBI agents are citified college grads who have little-to-no experience with firearms before they enter the FBI academy, so many of them had a difficult time qualifying with such a powerful handgun. Federal was the ammunition company that was supplying the FBI with their duty ammo, and the FBI asked them to develop a special light load for their pistols, because their pussy agents couldn't handle the recoil. The problem was that every ammunition manufacturer that loaded 10mm started loading their 10mm offerings based on the FBI light load instead of loading the 10mm to it's full potential like they used to. So now the BI had this big, single stack, 1911-esque auto-loader, but were shooting cartridges that weren't that much better than .45 ACP. So Smith and Wesson analyzed the situation, approached the FBI and said "We can take the 10mm, cut the case down so it will fit in a 9mm sized pistol, but keep the same bullet weight, velocity, and muzzle energy, and it'll give you a smaller pistol with higher capacity." That's essentially how the .40 S&W was born.
10mm guys like me call it the ".40 Short and Weak" or ".40 Short and Wimpy" because it's based off of the load data from the FBI light load for the 10mm. Because based on a 10mm loaded to it's full potential (right around 800ft. lbs. of muzzle energy, sometimes more) the .40 is "short and wimpy" in comparison (around 500ft. lbs. of muzzle energy). I'm not saying the .40 is short and wimpy compared to 9mm. I'm merely saying that I see no point in personally owning a .40 and spending my hard earned money on the ammo when modern 9mm defensive ammo is just as effective, while offering higher mag capacity, and lower recoil. If you like the .40 (and I take it you do, since you've taken this discussion like I insulted your spouse), then good on you. Shoot what you like. That's why living in a (relatively) free country like the United States is so great: personal choice. After about 20 years experience with .40 Smith and Wesson in several different makes and models (GLOCKs, SIGs, Berettas, Smith and Wessons that I've personally owned), it's just not something that I personally want to own anymore. I don't see the point when 9mm, .45 ACP, and 10mm Auto all have advantages over .40 S&W. Again, in my personal opinion based on my personal experience.
Guess what else I won't own after years of experience with them...GLOCKs. They're great, tough, reliable, reasonably accurate handguns, but they don't fit my hand well. I have to work harder to shoot well with them than I do other pistols. So I own H&K and SIG currently. SIGs, H&Ks, CZs, Berettas, and 1911s all work better for me than GLOCKs. In fact, H&K are really the only polymer framed handgun that I like. I usually prefer a metal framed pistol. There's no law that says I have to like what you like or that I'm wrong for not liking something. You do you, I'll do me.
