I don’t disagree with Clark’s two most prominent reasons but disagree with the priorities of them.
I think the Eagles wanted the $ to pay Slay.
I think they are confident in the Green Goblin–Mills– in the S role and think he will be quite a good value.
The Eagles probably plan to draft a S and need the roster spot.
I think the leadership factor is more of an issue on the D and especially in the secondary. Maybe a different vibe will help to develop the young CBs, especially Jones.
Finally the Eagles seem to be in a mini-rebuild mode. It makes sense to go with younger options.