What does Nick Sirrianni bring to the table??

I just listened to Hiefetz talk about Sirrianni and how the Eagles are only good when Howie picks the coordinators. They described him as a Dan Campbell type essentially, a vibes guy, a culture coach. But Dan Campbell is loved by his players and it’s obvious why, anyone can see what Campbell brings to the table and how that is beneficial to the Lions. But no one likes Sirrianni, Jalen Hurts hates him. Even with all the success the team is regularly on the verge of mutiny. He doesn’t call plays, and the more influence he has the worse the team gets. Why not fire him? Can someone tell me why they keep him around? It’s so strange to me that the winningest coach of all time who’s been to two super bowls in 3 years and won one of them is so hard to pin down. What am I missing? Does Howie keep him around precisely because he’s a non-entity? Does the eagles leadership prefer a coach who doesn’t really call the shots? I must be missing something