The president has broad authority to build his team and run his departments as he see's fit. Congress has the right to elect department heads but if a special initiative is created under the treasury department, that department does not need to be nominated. Elon has special overnment initiative to find massive waste... He has shown that the Social security database is de-duplicated and there are thousands of individuals above the age of 150. Hundreds of treasury employees have access to the same database he has, and most of the data analysis can be done open source via FPDS-NG.