Na página LoK Wiki de Tarrlok, podemos ver na seção de personalidade como eles explicam isso.
Due to the fostered belief that his father's failure was caused by his obsession with ruling the criminal underbelly, the councilman was obsessed with ruling from the top of power. His obsession to become the city's "savior" led him to commit immoral, if not illegal, actions, such as arresting innocent people under false accusations and kidnapping Avatar Korra.
Fonte: LoK Wiki