Here's my theory-

2016: Assistant coach Monty Williams wife dies in a car crash, children injured. Co-owner and founder Aubrey McClendon dies in a car crash. Conference Finals loss to the Warriors. KD Leaves for the Warriors. All this is in 6 months.
Somewhere around that time Clay Bennett is diagnosed with the life threatening cancer that no one will discuss.

This is where the team went all in to win a title before Bennett died. No expense spared. The window is only a couple years before the repeater tax puts the Thunder near $300 in payroll. The effort fails. April 24th 2019 Sam Presti starts talking to other GMs about trading Russ and/or PG, as well as anyone else on the roster. There is no action on Russ.

Russ will stay a few more years. He might retire here.