I'd argue Trump wasn't able to bring on any sort of competent Cabinet members as well as key national security and domestic policy advisors, because quite frankly nobody wanted to work or be associated with his administration and his incompetence... Those who were actually competent saw the writing on the wall and resigned by their own will (Nikki Haley), or butted heads with the president and were given the chop (Generals John Kelly and James Mattis). He never was able to properlly staff his administration, and as a result Trump was stuck with staffing hard-right personalities and party donors (Mike Pompeo and Kelly Craft) as well as Bush-era staffers that are way past their sell-by date (William Barr), forming the echo chamber of advisors as you mentioned.
With the Republicans looking likely to keep the Senate, I'm worried Biden might not be able to get the key Cabinet picks (Susan Rice and her Benghazi skeletons, Lael Brainard and her China/WTO ties) through committee hearing. Given Biden's age and mental state, it'll be an incompetent Kamala Harris and Republican-approved Cabinet picks running the show - same shit different day.
