In order to protect his people, Rick attempts negotiation and persuasion to stop Negan from killing and remain civilized with each community. Negan is the type of person who gets what he wants, he is always proving a point in everything he does. Alexandria, The Hilltop, and The Kingdom all provide supplies at Negan's request to prevent future problems between them and The Sanctuary.
At The Sanctuary, Negan is looked up to and admired. Everyone follows after him and even calls themselves Negan. Negan provides for them and keeps them safe although he is harmful to people outside of his group. He goes to the lengths of killing and holding Rick's people just to show what he is truly capable of.
In my opinion, season 7 played out perfectly in order to reach the same point in the comics. I have read the comics myself and know that Negan is only the beginning. The season 7 finale ended with Negan announcing the start of a war, comic readers know this as The All Out War. The action packed finale set up what has been greatly anticipated since the introduction of Negan. Season 8 will premiere in October and we can only wonder how it will play out and compare to the comics.