So a subsidy to stop building, instead of a subsidy to start building
No, it's compensation for backing out of a deal. In contract law, once a deal is signed, you're entitled to the "benefit of the bargain" if you perform your end of the deal. A breakup fee allows one side to get out of the deal, while compensating the other side for sunk cost into the project, opportunity costs from not having pursued other deals, etc.
I think you're missing the commenter's point.
...the point being the hypocrisy of exercising that option in the name of removing subsidized power, not the literal financial mechanism.
More like a bribe.
Trump literally just paid money (taxpayer money) for nothing
I don’t understand what pot of money this is coming out of. Has Congress authorized taxpayer money be used for paying energy companies to halt projects?
Republicans in congress have decided that Trump should not be stopped. Ever.