Berkshire Hathaway was investigated for insider trading, resulting in Sokol’s resignation. Four former execs of BK’s General Re were found guilty of fraud.
Almost all of those were done (temporarily) well after the fortunes were made.
Any examples you'd find I'd bet 95-99% were either the result of subsequent monopoly or as a result of government intervention either directly/indirectly benefiting them.
The 1-5% which weren't were likely punished. As the examples you mentioned were...
And Buffett was the richest man in the world well before either of these incidents.