Why is not redirected to home after login?

auth()->attempt($credentials, true) is working but its redirecting to /login however! I didn't do anything like that in middleware for example. Can anyone knows what is going on? Thanks

public function login(Request $request)
    {
        $this->validateLogin($request);

        $credentials = $request->only('email', 'password');

        if (auth()->attempt($credentials, true)) {
            // return 'it works';
            return redirect()->to('/');
        }

        return redirect()->back()->withErrors(['msg' => trans('labels.others.credentials_not_valid')]);
    }


//routes
Route::group(['middleware' => 'auth'], function () {
    Route::get('/', ['as' => 'home', 'uses' => 'HomeController@index']);
    ...

via Chebli Mohamed