“How can tax credits exceed tax paid.... ???”
They should not. Using the tax system as a welfare provider. Been that way for a long time.
See Obamacare insurance premium subsidies.
For MILLIONAIRES whose dividend and capital gains income comes in under about $48,000 - they are eligible for generous tax credits if they buy their insurance via their state’s online exchange.
(Flip side of this, if they make at least $1 over the cut-off, they lose this tax credit and pay substantially more for their insurance premiums. The so-called “obamacare cliff”.)