How can internal auditors have an independent mental attitude when they are employed by the company they audit?

Internal & External auditors has difference in scope of their work and that's why different independence levels are expected from both of them as external auditors are the auditors who has to provide their independent opinion regarding the financial statements of any company, they are required to display independence from the management of company while giving opinion about fair activities.

On the other hand internal auditors are the auditors who are appointed by the top management of the company to prepare and implement the risk assessment measures and to keep an independent eye on the overall operations of company that's why they are independent from operations of company and directly reportable to top management of company like shareholders auditor board etc so in this sense they are also somewhat independent from company as well.