Good for them for putting their money where their mouth is and standing up for what they believe. Also, this is a golden opportunity for multi-billion dollar tech companies to also do the same and match or double the grant money in support of PSF! Google, AWS, Microsoft, anyone?
I mean, it's also just the plain common sense move: accepting that money would just be putting a noose around their neck and handing the other end to the Trump administration. (And there is a 100.0% chance they'll just claw it back eventually anyway.) It's a shame that months of NSF grant-writing work was completely wasted though.
Pretty much every "negotiation" with the Trump administration seems to work that way: An iterated prisoner's-dilemma, where any cooperation from you just means they'll betray you even harder next time...