It's not about Carraway's involvement now, but about what actions he took that the company is still responsible for. When you buy a shell, you take on all the baggage of the shell, which is why most lawyers don't recommend it. Especially when you have a shell which already has an ugly past.
Buying out the shares of all prior owners, let alone all, does not absolve the company of any liability or responsibility for the prior owners' actions.
The only thing necessary for the triumph of evil is for good men to do nothing.
EDMUND BURKE (and others)