Coke literally had a small amount of cocaine in it, as a stimulant, prior to new coke being released. It was grandfathered in, still allowed at that point.

New coke was released, because they were being forced to change their formula. Some say they released new coke, knowing they'd have to re-release old coke, but that by that time the average person would not accurately notice the taste change.

A friend of mine, a coke fan, kept a case of old coke. He tried the newer-old coke, side by side...

It didn't taste the same.

Some say new coke was a wild success. Loads of media attention, and they dropped the formula change in without notice...

Coca-Cola hasn't contained serious levels of cocaine since 1903, although it did use some coca leaf extracts up to New Coke, but that is not the same as cocaine just as poppy seeds are not the same as heroin. It's not clear that they were "forced" to remove that.

The New Coke story is quite interesting, but I don't buy in to most "explanations" of it. I think it's far more likely it's a case of "competitor X is more popular! We need to do something! Let's copy competitor X!" This is a classic business mistake, because customers are choosing you instead of X because it's not X, and if you merely copy X you lose your value.

I thought it was because they switched to HFCS?