The United States has an almost uniquely punitive and unforgiving justice system, hence it having the largest prison population in the world, far beyond even a significantly more populous (and unapologetically authoritarian) country like China. Most other developed countries' justice systems have far shorter sentences and a lot more opportunities for second chances.
They didn't "disappear", they just didn't show up to testify, and didn't admit to having been intimidated, which is what was implied in that video, and like it or not, without any evidence to support a charge of witness intimidation there's not much the justice system can do, and by this point the statute of limitations is up on such charges. (That's a thing in all common law countries such as the US, the UK, and Canada)