Why did the period of detente not succeed in ending the Cold War?

Hi there, so what i know is:

as détente broke down, progress on nuclear arms control stalled completely. As their relationship continued to erode, it became clear that both the U.S. and the Soviet Union had overestimated the extent to which détente would contribute to an agreeable and peaceful end of the Cold War.

I hope this helps! And remember to always give me feedback if I got it incorrect, I promise I will make up for my mistakes :-)

                                     - Haley <3

can someone just answer this