Earlier quoted context omitted.
I imagine it's on account of all the administration and intermediaries.
It's not. There's a good breakdown that compares what drives healthcare spending between the US vs Germany (and others). https://www.healthsystemtracker.org/brief/what-drives-health... The vast majority of the difference comes from just the raw cost of inpatient and outpatient care. Even if you were to completely zero out the administrative costs per capita, you'd hardly make a dent in bridging the gap.
Looking at the article, it's pretty hard to understand what what's actually costing more. "Inpatient and outpatient care" is a pretty enormous bucket and probably accounts for a whole lot of salaries, services, and such of pretty much any job title with "medical" in it.
Admin, does in fact represent the largest % difference... but it's not clear what's grouped into it. I assume it means government departments, insurance firms, external legal/finance services. I don't think the data refers to a salary-bysalary breakdown of costs.
Sometimes it's best to look at these things from the ground up. Doctors, nurses. How many? How much are they paid? Is the diff more or less than mean diff? If no, move on, If yes, dig deeper.
You really can't even rely on price data to tell you much. Most of these markets have a broken or absent price system. The underlying answer though, inevitably will likely be "because they're run differently."