While there are many theories and studies concerning the end of the Cold War, circa 1990, I postulate that one of the contributors to the result was the development of adaptive optics. The emergence of directed energy weapons, specifically space-based and ground-based high energy lasers made practicable with adaptive optics, showed that a successful defense against inter-continental ballistic missiles was not only possible, but achievable in a reasonable period of time.
Robert K. Tyson, Robert K. Tyson,
"How adaptive optics may have won the Cold War", Proc. SPIE 8725, Micro- and Nanotechnology Sensors, Systems, and Applications V, 87250S (29 May 2013); doi: 10.1117/12.2010801; https://doi.org/10.1117/12.2010801