There's another problem that arises when you have too much wealth accumulate under the aegis of a single concentrated power, a power which is to properly dispose of that wealth to maintain its propensity to accumulate. This is less some sort of decadence theory or an account for the transformations wrought by the inflow of what finance today would call "hot money," and those are phenomena that themselves are worth looking into. No, for now I just want to comment on a simpler logistical and organizational question of how wealth is actually distributed and put to use.
Just think of a massive hoard of gold: what exactly can be done with it? The larger it becomes, the heavier it gets, and the more space it takes up, making it more and more difficult to store, and moving it and distributing it becomes ever more labor and energy intensive. One imagines the treasurer standing there, overwhelmed: "what are we going to do with all this shit?"
Back in the ancient world, the best time for clever defenders to attack raiding foreign forces was when they were fully encumbered with all of the loot they had amassed, weighed down and distracted. The Byzantine forces - much more cautious after their huge 7th century tumble - were known for doing this to the Arab raiders, among other forces.
All that wealth! You can pick up all sorts of heaps of treasure and load them up on your beasts of burden; I bet it looked pretty good gleaming in the sun too, but it wasn't going to do anyone any good until that loot had landed and was plugged into existing power structures of the raiders themselves, giving the loot the chance to be distributed in service to various flows of human labor and endeavor.
The form of wealth matters, and how that wealth is operating in a given context. Gold needs to be run through human labor, furnishing food and drink and shelter say, by the guarantees of an overseeing sovereign, and then that furnished labor is ultimately combined with raw materials to be transformed into swords and spears and axes, to be of any use on the battlefield anyway. Not so easy fighting them back brandishing a chunk of bullion. And all of that takes time, and coordination, and knowledge, and talent.
These are slightly more complicated wealth metaphors for understanding something happening in the modern world, but here is an even simpler one: you can easily choke out a fire by piling too much wood fuel on it. A good fire needs the circulation of air to get the heat and the chemical reactions to the wood fuel. Piling on too much fuel is a good way to smother that hot core, isolating its radiating energy, and eventually it weakens and burns out and dies long before it reaches more fuel sources. The wealth lies not in just the hoard of wood fuel, which only represents potential fire, but the entire process in which the fuel is set in a proper relation to the heat and air which allows for all of the elements to react together to produce more heat and light.
So on to the modern world then. The United States has been described as the most powerful nation in history, with the greatest known hoard of material wealth to show for it. But something has been happening for decades that is incredibly baffling and distressing to watch for anyone not enclosed in the shrinking and concentrating bubble of the ruling classes.
The US has been squandering its wealth and goodwill - both within and abroad - for some time now. The strip-mining of the developing and undeveloped world, reflected inwards as a stripping away of domestic wealth also, has only intensified and accelerated, moving ever outwards to groups previously thought of as somewhat protected, such as allies in foreign policy and higher classes domestically.
Domestic infrastructure and global good will advances in a sort of desiccation as financial power especially concentrates in towering and preposterous pyramid schemes which eventually flame out, taking out the fictional wealth and attached collective trust with it.
Take the F35 program - or similarly the aircraft carriers - which is emblematic of military wealth and power, and yes the technology represents a massive concentration of wealth over space and time. The technologies themselves are incredibly sophisticated and are produced through sprawling interconnections of technical suites and material flows, built up upon generations and generations of knowledge and cumulative technological progress. These weapon systems in isolation are quite dazzling and impressive in a limited technical sense, but they can't do much of anything on the battlefield and are plagued with functionality and maintenance issues. The wealth itself is piling up and setting up, standing forth in a useless form in its targeted context to then be destroyed in a real fight, just as all of the nations real wealth is being squeezed out of the greater body politic - now like juice from stone - to be taken up into high finance and then evaporated off as the disconnecting and insulating ruling core is sectioned off and dies, separated from the rest of the wood fuel.
Ditto if you look at the greater tech platforms, including the increasingly dysfunctional and obnoxious social media - systems descending into a sort of bewilderment as they are iterated by their bewildered technicians and programmers, who become ever more bewildered and lost as they partake in the bewildering systems themselves, systems that in their cyclical iterations become more and more lost with the garbage coming in and then going out. Echoes of Tainter's complexity theory perhaps, but one aspect of these greater processes to be mindful of.