But the Saviors started it when they started extorting places like Hilltop.
Rick's folks inserted themselves in a situation.
But dont act like the Saviors were angels or something. The Saviors are gangsters and Rick's group tried to stop them, but they had more manpower than Rick counted on.
No, they did not insert themselves. Negan's people were already attacking Rick's group. It's just a lucky thing Abe found that rocket launcher, or he, Daryl, and Sasha would be long dead by now.