"If you or I wanted to quit our jobs and move abroad in order to offer a better life to kids, that would be pretty simple. Millions of people do this. Why shouldn’t they"
That's not what they're doing. As @Bluntness100 points out, they're not quitting their job in the traditional way that you and I would.
They are taking their department within the family company, and spinning it off into its own legal entity and subsidiary, without consulting anyone in the Group but still drawing upon funds associated with the Group, benefitting from Group premises, pooled resources etc.
That would be considered downright outrageous in the corporate world, and wouldn't even make it past the Legal team let alone the reaction from Compliance, the board, shareholders etc.
They're not simply "quitting one job for another and a new life for their family".
They're running off with a chunk of the family company, and immediately creating a new entity, hoping that the momentum of doing that will mean the Group has no alternative but to issue a statement dissolving the Sussex "arm" of the company and allowing it to operate as an independent and not a subsidiary.
Ridiculous, arrogant and downright wrong are words that come to mind. Not "let them enjoy their new life".