'Fact-based' generally implies 'lesser impact', it's way easier to catch eyeballs with fakes and click-bait than with better stories, and part of the fake news issues is that professional success in journalism is dependent on impact, not on accuracy (a similar thing goes on in academia).

You'll have to figure out a way to increase the impact of writers with more accuracy (less negative fact checks maybe?) by promoting them in some shape or form. Have you considered top writers scoreboards or something similar?