I think in your example to "play off" is to act in response to or benefit from, like using the popularity of the X-Files to promote one's own show or opinion. See also piggyback as in "Piggybacking on the popularity of the X-Files, the CIA..."
In another context it might mean to discount, or distract from, like when someone is accused of something and though they may be guilty they "play it off" as a dumb question. See also downplay
Your example starts with "While..." which doesn't read quite right so it's unclear which context is intended but I'd go with the first one.
Hope this helps, Starrover!