Perhaps what they meant was that CWD makes the infected animals more likely to be eaten. Then the apex would, over time, kill the affected subpopulation.

Not sure that this was meant and if that even makes sense.

Culling is vital to healthy populations and balanced ecosystems.

Animals don't have medicine, so the sick or diseased amongst them can spread susceptibility to illness more readily, over time making groups more genetically or immunologically prone in a way that could lead to destabilization, become vectors for contamination (some cancers are contagious, like in dogs, and prions don't break down easily, making them true ecohazards), or end up as vectors as they contact other animal populations (HIV and swine flu were non-human origin).

Predators also encourage migration of herds, so deer won't consume an environment to depletion, including crops.

Predation is nature's free labor!

Kill and eat the sick, reducing the spread of the disease.

There's a study that showed mountain lion (puma) can eat and digest CWD infected deer meat resulting in > 95% removal of prions. Don't quote that number though, some googling should find the study.