Toph becoming a cop is actually a materialist reading. She's a noble who went through a rebellious phase as a child, not even a teenager. Her material conditions brought her back to her wealthy, exploitative upbringing. Her proximity to several leaders of nation states, her family wealth/status, and her literal "only person in the world" metal powers brought her to the natural conclusion that she needed to preserve the powerful elite she and her friends were part of. Naturally as an innovative, intelligent, and adventurous person she saw how the old world system was transitioning into bourgeoisie capitalism and instead of getting swept away with the old aristocracy she secured an essential position as chief defender of capital.

Jk Toph deserved so much better.