Thompson wasn't personally accused of any wrongdoing, this is an antitrust probe of a corporation. It will continue on no matter who's the CEO.There may have been vested interests that didn’t want him to be probed depending on what else might come out. Seems like a killing where big money was involved, thus requiring a professional hit away from his home turf. Not a disgruntled patient or family turned away by UHC. No, this was more personal to Thompson even if it involved his business dealings. JMO.
And this stuff is just par for the course in corporate America. Justice Department investigations happen all the time. Off the top of my head, Google, Microsoft, Apple, JetBlue, X, LiveNation, RealPage are all companies that have either current or recent antitrust actions by the Justice Department.
And even if violations are found, it's a long, involved process to implement any changes, complete with federal court cases, etc. And there's a good likelihood that the Trump Administration will discontinue the investigation anyways.
So, I really doubt this has anything to do with the CEO's death.