"" The initial vetting is handled by hundreds of program officers, all experts in their field and some of whom are on temporary leave from academic positions. ""
Also, NSF program officers can have conflicts as well, for example if you are on leave from a university then you can't be heading a review panel that has any grants related to that university.
At my university, we also have to do periodic online training about conflicts of interest, and have to fill out financial forms disclosing whether we have a financial stake in the work (e.g. if we own a startup and are trying to direct research funds to that startup).
Basically, I've always felt that we held ourselves to a higher standard than Congress held itself too (e.g. being on a Congressional oversight committee and owning stock in affected companies, but that's a different rant).
The changes being made now will deprofessionalise and politicise large parts of the US civil service. The US will be poorer for it.