It's maybe me, but in the dramas I'm recently
devouring watching, this word pops up often. I bet everyone who watched few shows knows this word. And I bet everyone can picture what chaebeol is. And what chaebeol is not (yes, Taoist wisdom speaks through me, no connotation, wild ladies!). Some may say it's the same as japanese keiretsu, but it's not true. The main difference is that chaebol companies are run by one family. And keiretsu is run by an assembly of associates. After Japanese left Korea after occupation, first chaebeol were created, both as taking over what was left of japanese companies or some started from the scratch.
When the military rule took over in 1961, they wanted to eradicate all remnants of Syngman Rhee's policy, including the corruption among the high finance world. Some were put into the prison, but military junta, I mean government, realized that the development is not possible without the cooperation, so some of those accused people had to pay huge fines and were exempted from the sentence.
Chaebeol could grow because of foreign loans and preferable treatment. From the very start, they specialised in manufacturing, trading, and heavy industries.