They're simply trying to eliminate most academic research, there aren't many other plausible explanations here. Blocking the grant reviews might look temporary, but these delays pile up and at some point it simply won't be possible to properly review the grants in time.

And this is not the only way they're interfering with scientific research, the hard cap on indirect costs is probably the other most significant event. And all of this is on extremely short notice (or actually retroactive as it applies to grants that are already approved), which makes it even more destructive.