When you start a Modern And Progressive Burger Company, or a dadaist Italian sandwich concern, you have options to scale out. You can invest your own capital and limited attention to open and run new stores (the Chipotle and In-N-Out models). Or you can “franchise” - a nominally separate organization pays you for access to branding, the correct supplies, etc, but for the most part is responsible for their own operation.
As they go about their business, they are nominally constrained by the need to preserve a united facade - one talks of going to “Burger King”, not “Jim’s Regional Franchise LLC”. Corporate can force them to participate in promotions, preserve uniform decor and uniforms, even jerk them around on what they pay for required supplies. But fundamentally you cannot just shut them down, and their actions are more driven by aligned incentives and explicit agreements than diktats from on high.
In many ways this is also a model of political power. The most direct analog is tax farming. Low state capacity means Rome cannot send a horde of bureaucrats to assess the requisite taxes on every ranch in Syria. What you can do, though, is delegate the job to one guy - he pays the treasury up front, and gets his end over time from the peons. Of course he hires some help, and they in turn might take a cut on commission, either explicitly or via the kind of corruption you expect when you’re dealing with revenooers in the middle of nowhere.
But this doesn’t end just because you actually do have the technology, in theory, to track the sale of every parcel of property in the country, or for that matter every payment for anything. Focusing purely on the money might work if you’re in essence ancapistan with an army, but contemporary government have a much more nuanced set of political goals and constituencies.
Take for example the banking sector. The pretense that Bank of America et al are private company, maaan, is paper thin. In reality there are a half dozen different agencies that give them Very Strong Suggestions about how to operate their company. You know you have an obligation to avoid Unnecessary Risks, don’t you? Well, we’ve identified Unusually Risky Customers. Can you justify those, sir? Are they disclosed? Do you have proper reserves for them? Shouldn’t you be using your limited resources to make different, safer investments, with our guys? BTW, have you seen any suspicious activity lately?
In exchange for this kind of Godfather-esque partnership, banks are given the legal ability to write loans out of thin air, a subsidized market for those loans, access to federal backstops of potentially unlimited size, preferential access to government securities, and so on. They are, in essence, franchisees of the money power of the Federal Reserve and more broadly the US Federal Government, with Federal Reserve Notes swapped for McNuggets.
But even inside the government, the idea of the Unitary Executive is observed more in the breach. Actually reading legislation and the US Code is often an infohazard unless someone is paying you, but if you do dive in you will notice quirks everywhere like “the Secretary, or his delegate, shall…”, and barely any mention of this supposed Executive. Congress seems to think that agencies and departments are the fundamental atoms and molecules of American governance, with the President at best exercising some latent and limited discretion to choose between available alternatives during the nominating process. If Jensen Huang steps in front of a bus, Nvidia drops by 20%. If the President strokes out - well, is Pepsi okay?
This isn’t just a stylistic quirk. There is fundamentally not enough attention available for the President to be actually involved in the business of governance. There are too many jobs available just for explicit appointment to be populated by anyone’s personal rolodex, or even by friends-of-friends. Even if the President “sets priorities”, to what extent can he actually enforce them? The Trump administration demonstrated the lack of recourse - and this is an intentional feature.
In reality the model here is that Congress is divvying up the portfolio of American governance and franchising it to semi-private organizations. If they don’t follow the law, theoretically the remedy is to sue them, or have your Congressman annoy them. You don’t get to vote them out. You don’t even get to vote a new guy in (again, cf 2016-2020). Presidents routinely find it easier to jack around responsibility between Defense, State, National Security Council, Treasury, and CIA in the conduct of foreign affairs than to actually get some particular department to do some particular thing.
Thus you end up with tiny little domains of absolute authority, where some guy has a stranglehold over some aspect of public life. It’s obvious what he gets out of it - money and power. What does he give for it?
In a patronage system, he would be kicking up money and some kind of electoral service. In our model of political franchise, it’s a much fuzzier kind of loyalty. He is generally the right kind of person, and so he is expected to behave correctly, even if we’re not so crass as to insist upon getting-out-the-vote on election day. And his loyalty must ideally be to the institution - this doesn’t mean he can’t be manipulated if someone does actually have enough control to use the institution for something, but in the basic case of institutional self-propagation and self-protection he must be ruthless in preserving the prerogatives of the agency itself. That means always visibly doing something, and demonstrating the right of the agency to do what they want (especially if nonsensical - no one needs an excuse for a good idea). And that in turn means, largely, data collection and holding the sword of Damocles over your “regulated entities”.
Carving the business of the federal government into these fiefdoms is in effect the same kind of limited incentive-alignment you do when you can barely get a letter to Damascus. You want EPA-type stuff done, so you spin up an EPA and staff it with the kind of people who think EPA-type stuff is just great, under the implicit assumption that they will just kind of run themselves in their own interest. If they go completely off the reservation, there’s always legislation and courts, but you’re not expecting them to be a paragon of efficiency and mission-driven internal governance. You’re just expecting them to do EPA-type stuff, as a process.
What you are not doing is giving “the President” the authority to actually solve a particular problem, or even do anything in particular about a problem. At best he is a train-engineer, setting the speed and occasionally applying the brakes, on a route with a defined start and end point, while the passengers go about their business in the back.