https://www.macupdate.com/app/mac/23049/smcfancontrol
The hard drive died from heat. Before it went completely dead it would work when the computer was cold and then stop when it heated up enough. Afterwards I found this freeware which lets you override the default fan settings, it kept the replacement drive alive. I think part of the problem is I used it for gaming and that made it hotter than most iMacs which never get used for that.
Your linked third party app is intended for MacBook laptops, not iMacs, nor does Apple recommend its usage as it will make the fans run at full speed when they are not necessary.
You keep right on dancing with your claims about iMacs being made of laptop components in desktop cases. I posted PHOTOS of the internal components of the very computer you claimed was laptop components proving YOU WRONG. You can make those false claims but they are just that FALSE. Hard drives can fail for many reasons. They have a "mean time between failures" but that does not mean there are not some that fail right out of the box. Your claims that Apple puts laptop components in all iMacs, especially the one you had as you specified, does not hold true.