No competent chemist could have ever thought that BPA is a safe substance.
Some chemists have believed that the risks of depolymerization for the plastics that are made with BPA, e.g. polycarbonate, are low, so the risk of BPA leaching into food is low. However there have always been many chemists who have believed that the risks are too high for any such plastic to be considered as safe for food contact.
The problem is that the relevant true experts are almost never consulted for decisions regarding the use of materials for various purposes. Those who are consulted have usually very narrow specializations and can have informed opinions only about a part of the relevant criteria. The final decision about the use of materials is usually done strictly by financial criteria.
Some chemists have found a method to make polycarbonate, a plastic that combined useful properties, like high transparency and high impact resistance. They did not think about which are good uses for it and which are bad uses for it, it was not their job. Then someone else has developed a cheap method to make bottles out of it, also without giving much thought about what is suitable to be stored in such bottles or not, it was not their job. Eventually someone else has decided to fill PC bottles with some beverage and sell them.
The error has been at the end, because any material used for food-contact should be scrutinized much more than for almost any other purposes. There already are laws and regulations about materials for food-contact, but they are neither strict enough, nor applied correctly most of the time.
While there have been many problems with plastics used for inappropriate purposes, there are a lot of similar examples with all kinds of materials, crystal glass with lead used for many centuries (fortunately only the rich could afford it), silver-mercury amalgam used in dentistry for more than a century, uranium glazes and many others.
We can only learn from past mistakes and improve the existing legislation.
In my opinion, the most important would be a law forcing any manufacturer to publish the exact chemical composition of any material that is used for food-contact in their products.
This actually does not leak any valuable trade secret. Anyone with enough money can make a precise chemical elemental analysis of any object, only individual customers cannot afford it.
The valuable trade secrets are in the details of the manufacturing process, not in the final product, which can be analyzed by any competitor.