In a publicly traded company you get to chose whether to buy or sell the shares of a company based on how the CEO is running the company (including who he appoints to audit it)
In US Govt, we don't get to chose whether to "invest" in the govt or not, our taxes our collected by force.
So instead we have the power to vote for people in congress (who decide home much taxes are collected on how they are spend), and the president (who can execute on the spending directed by congress, but also has the power granted by constitution to audit and spend effiecntly)
The US Govt Shareholders (Voters) have SPOKEN, and SPOKEN LOUDLY! (Electoral College victory, and Popular Vote victory). They elected republican majority congress, and President Trump. Thus the voters voted for a deep gov't audit headed by Musk (Trump publicly campaigned on auditing and cleaning up spending, and publicly stated who will be in charge of the audit).