IBCs are bare-minimum companies. They don't require resident directors or resident shareholders, are exempt from all taxes ("ring-fencing" of taxes), and have no filing requirements at all. They are usually also associated with no or limited public disclosure.
At the time, some of these were novel concepts in many countries.
BVI passed this act in 1984. Not much happened as︀ Panama was still the leading offshore incorporation jurisdiction. Things changed in December 1989 when US︁ troops invaded Panama to arrest president Manuel Norriega. From the early 1990s, BVI took off︂ enormously and became the new leader, which by most metrics it still is.
Developing or︃ poor, often tourism-reliant, countries across the Caribbean and parts of Africa and Asia-Pacific , many︄ if not most of which shared a kinship with BVI through past colonial rule by︅ the British Empire , began to basically copy-paste the BVI IBC act as a way︆ to help fill the government coffers with a steady flow incorporation fees and annual renewal︇ fees. Brunei also got into the game, despite already being wealthy.
That's how IBC spread︈ across the world. It was basically a blueprint for printing money and it worked well︉ for about one or two decades.
Nearly all of these IBC acts are still in︊ effect, but most have had to make changes to appease OECD and such.
If I︋ recall correctly, Brunei, Niue, Dominica, Montserrat, and Saint Kitts (but not Nevis) have repealed their︌ IBC acts and not replaced them with something similar.
Bahamas, Belize, BVI, and Seychelles have︍ changed their IBC Acts quite a lot but functionally, what they have is still very︎ similar to a classic IBC. Some like Saint Lucia still have their IBC Act but️ have removed the tax ring-fencing, so that the standard tax law applies to IBC. It just so happens that the countries have also switched to territorial tax systems or , even if not , still market IBCs as tax free provided they don't establish tax residence there.
Mauritius is always the odd one out. It never had an IBC Act but it had something similar, which was repealed a few years ago and replaced.
Compare this to Cyprus and Hong Kong, where all companies are formed under the same law. No IBC Acts there.