Chris has shown interest in unexpected games before, remember him moaning about Barb complaining about the violence in Resident Evil Revelations?
Destiny's had a huge Sony backed marketing push, so he probably see's it as the poster child for this new gen or something.
There's not really anything there for him to not like I guess: The gameplay mechanics are sound and it's fairly forgiving towards those who aren't normally that into fps's.
In fact, I can see him getting hooked by the skinner box mechanics and happily running through the same area repeatedly in the quest for gear. It's actually a pretty solid choice for somebody with literally nothing to and a tenancy towards monotonous time sink actions.