What factors pushed the nuclear arms race, which held back and facilitated the negotiations?

The nuclear arms race in the 20th century was driven by the confrontation between the two systems. The capitalist and socialist way of life of the people. Since, in essence, these two systems are antagonistic, an uninterrupted arms race was inevitable. Two deadly enemies, they will always build up their weapons. The only restraining factor was that there could be no winners in this war. With the collapse of the USSR, when the current regime became friendly to the United States, the arms race automatically ended.