It would be the end of innovation.
What would no longer be rewarded is parasitism.
At any rate, if a company found a cure for cancer the stock market would absolutely skyrocket in a way almost never before seen. It's unbelievably hard to imagine how a company finding a cure for cancer would be to the detriment to a diversified portfolio.
Even if it's a tossup, does that mean there's a 50% chance of the inventor of such a cure being liable for that crash?
The issue here is that it's not a tossup. The probability is >=2:1 hence the liability, even if that is alive after the plunge.
The specific complaint is that Meta ignored the concerns raised by its shareholders about the impact of its actions on the broader portfolios held by its shareholders.
Once again I do not think this case has merit, and lawsuits of this nature almost always fail, but we should at least take some time to understand what is actually being pled so that we can object to it with a firm standing.