I think most takes on this are overly reductive. The whole situation is sad really.
The root cause, to the extent that one exists, is that no one is accountable for successful execution in a very literal and systemic way. Some parts of the government I've worked in are worse than others, but it is endemic. This leads to a textbook case of Pournelle's Iron Law. There are no negative consequences for a handful of people aggressively maximizing their personal benefit and acquisition of power as their primary objective. This is how you get the fiefdom-building, feather-bedding, and the usual revolving-door corruption that these programs are notorious for.
Most people involved in these programs aren't like that but enough people are that it is impossible for people trying to do their jobs competently to get anything done. The people that defect are the people that end up controlling the programs because that is how the incentives work.
Inefficiency and corruption are a symptom, not the disease. The incentives virtually guarantee that these programs become playgrounds for sociopaths. Average workers on these programs are put in the demoralizing position of either having their good effort constantly undermined by leaders that don't care about the mission and are openly making decisions for personal benefit or to defect to the side of the sociopaths so they at least get some personal benefit out of it. Most of the best and most competent people I know eventually leave Federal service entirely.
A second-order consequence of this is that over time, no one competent wants to work on the programs that are run this way. Through churn these programs slowly fill up with mostly useless seat warmers who don't mind a job where no one expects productive outcomes. It is a kind of stealth UBI for government employees. Some people request assignment to these programs.
You never hear about the programs where the leadership is actually competent and cares about the objective because these actually function pretty well. But the incentives are such that this is the exception rather than the rule.
I'm not even sure how you would fix it, I suspect it is politically impossible. When companies become overtly like this they tend to slowly self-immolate into irrelevancy. Governments lack these negative feedback loops in any meaningful sense.