What did abandoning the forts produce?

The immediate answer is peace — at least in the Powder River Country, for the period between 1868 and the resumption of conflict in 1876.

The Lakota and their allies continued to hunt in the unceded territory.

The treaty was generally observed, at least in its core provisions, for several years.

The longer answer is more complicated.

The abandonment of the forts was not the beginning of a genuine accommodation between American expansionism and Lakota sovereignty.

It was a pause — a period in which the immediate pressure was reduced while the underlying forces that had created the conflict continued to build.