Note: this is me explaining what is happening rather than explaining the causal chain which the NYT thinks is happening, because my version is a lot simpler and more likely to be correct.
Actually, I'd expect rolling blackouts long before an actual Al shortage.
(Reasoning: Aluminum is one of the most abundant metals in the crust, but it's never found pure. It's always found in an ore, and the cheapest way to refine the ore is very electricity-intensive. As a side note, aluminum was once a fairly expensive metal; the tip of the Washington Monument is made out of it, which was an extravagant expense at the time.)
Goldman is one of the largest -- and therefore, most effective -- players, but basically Goldman and its ilk have been using their financial (and legal) clout to essentially corner commodity markets. They are creating effective monopolies for themselves -- or sufficient control to significantly influence availability and therefore pricing.
In this particular instance, as far as I read, they are using their control of aluminium stocks and warehousing to jack up the prices they receive. This may abut regulatory and other concerns, resulting in a "shuffling exercise" to place their price increases within boundaries and definition of an established market mechanism and regulation.
Still in the process of being converted from a public resource to a private commodity -- in the U.S. and some other countries, at least -- but another one to keep an eye on is water, including potable water. There are companies working to privatize supplies, with an eye to charging you whatever the market will bear. And if and when they control said market? And given that most communities are single sourced for local, bulk delivery?
Taxpayers pay representatives to represent Goldman while paying billions upon billions in extra costs for nearly every function in life.