ish - I can only provide informal remembrances. I would say there was virtually no connection to the B&W / political change. Thiel didn't pay much attention to that stuff. The dealers variously aligned with various manufacturers, but Thiel / Kathy didn't get involved with those dealer decisions unless asked for product-performance / sales success advice.
You're on the right track with product-performance drift. Dave Reich's DR-series amps were extraordinary in performance / price at their time. After he left, the amps kept the basic circuitry, but drifted into euphonic design territory, which didn't serve our needs as a manufacturer. We sought out very linear, neutral, high-performance gear. Bryston continually worked in that direction as well as being rugged and reliable. Jim used Bryston in the lab as his reality check against the big, expensive workhorses.
I personally never felt the Bryston gear provided the nuance and detail that our products could deliver. We used it at shows to demonstrate high performance / affordably priced capability. Reviews and rumor suggest that their present cubed series steps up their performance quite a bit. Good people, good gear.