The house needs to be cleaned this summer, it’s clear by now if it wasn’t years ago. Shanahan needs to go, the entire coaching staff needs to go, and at least two of the core 4.
Sit Tavares and Marner down, tell them you would like them to waive their no-trade clauses, and you’ll do your best to find them a destination that is to their liking but you can’t guarantee anything. If one or both refuse to waive, then you simply let them walk at the end. I’d also strip Tavares of the captaincy.
At which point you have Pelley (or whoever the new president ends up being, or even Treliving) hold a press conference and state simply that the culture is about winning, and finding players who want to win. When Marner and Tavares walk, or are traded, the fans and media will fill in the blanks.