I thought this too, but after reading some of the other comments here I read some of the text of the chips act and the 2021 NDAA (mostly section 9902) and AFAICT Congress appropriated a bunch of money for financial assistance for semiconductor companies and gave the Dept of Commerce the authority to determine the funding type.

That they were grants instead of any other instrument appears to be a Biden Commerce decision, not a congressional one.

I’m no lawyer and could certainly be missing something i the law that says it has to be grants but from what I see it looks like figuring out what to do the the money was pretty much delegated to dept of commerce with limited direction about eligibility and review criteria.