They knew the risks ten years ago, twenty years ago, thirty, forty, and fifty years ago, but that didn't mean there wasn't room for safety improvement and didn't mean we had no business improving safety. Knowing the risks doesn't dismiss them.
Helmets only help with minor impacts. It doesn't do much if something large hits it, like a wheel, it does nothing against striking a fence at race speeds, and doesn't prevent a
driver's head from being knocked off by a fire extinguisher. A couple years back there were wrecks wherein one car glided across the top of another, as in Monaco, and at that time I figured it was just a matter of time before the angles would be right for a decapitation, and all the helmets in the world can't prevent a car across your cockpit from knocking your block off.
The regulations didn't mandate the bump. While it is a result of a regulation change for 2012, the regulations don't actually require that specific configuration. This post made it sound like it was actually required to comply with the 2012 regulation changes, but I just want to make clear that it wasn't.