Not sure we need overthink the shell reference.
It’s not capitalized.
One definition states, “b : the hard or tough often thin outer covering of an egg”
Q mentions the pyramid just the line before.
If you remove the side of a pyramid it collapses.
If you crack a shell, the tender inside is exposed.
The 3 remaining/controlling families are the shell to all those under their control.
Remove that shell, break that pyramid and the tender goo within can be easily accessed.