With respect, I think your take on this particular matter sounds awful.

Negotiation and persuasion are very important parts of being a wise leader in technical and creative fields, but it sounds like OP followed exactly what you advocated to no effect.

None of us were in the room with OP and know both sides of the story, but it sounds like he gave them 2 months of the very kind persuasion and negotiation that you're advocating, and the employees persisted as willfully insubordinate and not following the processes that their boss wanted to enact.

Do you keep negotiating for another 2 months? 2 years? Or do you have to make a choice at some point that people aren't even attempting to try and learn the processes you were hired to implement?