If you kill an oil executive, a new one will take their place. You've gotta go after the company instead, that'll have a more direct impact and be harder to replace, especially if paired with regulation.
That's why you keep doing it. Eventually a chilling/deterrent effect will take hold. It's not like anyone's actually passionate about oil. They can go be apple orchard execs or something idk
This is definitely not a hill I want to die on, but there are three axes to deterrence:
Certainty of punishment
Severity of punishment
Celerity (speed) of punishment
Basically you can't just raise one axis and expect anyone to be deterred. So if you just put to death one random exec it's probably not even as effective as, like, slightly maiming a handful. Or cream pie to the face of a hundred. Or a gentle yet stern tap of the wrist of a thousand.
CEOs may be sociopaths but they have a more developed sense of self preservation than your run of the mill murderer so it might be more effective IMO. I say try it and add the death penalty for severe financial crimes like they're doing in Vietnam.