Deeming a drug safe is much easier than deeming it effective.
One thing most people don’t understand is that the hard scientific costs of drug development at a scientific level are usually millions of dollars, not billions.
What happened in the late 50’s and 60’s was the birth of children with limb malformities/malformations as a side effect of using Thalidiomide, a cancer drug. It was a huge problem.
The thalidiomide crisis exploded into a blowback style reaction that would inflate the cost of drug development to Billions of dollars and make patent lawyers rich.