Imo, you can't really compare NPR in 1999 with NPR in 2024 - almost everyone who was senior in the organization back then will have already retired 15-20 years ago, and their funding structure today is much more donor and advertiser driven than it ever was in the 1990s.
Trust comes more easily for individuals / news organizations / political groups when we're all more focused on the framing of arguments on their own merits, with less focus on the in-groups/out-groups of who those arguments are against or who they are supporting.
Also the source doesn't back up the claim at all. The linked article:
1. Isn't about NPR. It was about some affiliate Corporation for Public Broadcasting TV stations.
2. Points out it wasn't exclusive about selling to democrat campaigns. As mentioned in the article, Bob Dole's campaign was involved.
Regardless, know you know. And knowing is half the battle.