Kamala Harris appoints her campaign chief; why is it being criticized?

Vice-President Kamala Harris who is also the presumptive presidential nominee of the Democratic party has appointed Jen O’Malley Dillon as the new campaign chief. She had earlier served as the campaign chief and had ensured Joe Biden’s victory in the US Presidential Election in 2020. The recent events surrounding Biden has been severely criticized and hence this appointment of Jen O’Malley Dillon is not being viewed favorably.