...and furthermore, look why the permanent five members of the Security Council are who they are; the US, UK, France, China, and Russia.

Answer: They were the nuclear powers of the time.

It should also be noted that the two superpowers engaged in successive rounds of arms reductions through the 80s and 90s.

Those treaties continue with even further rounds of reduction being offered. That despite there being only one hyper power, and no superpower to fill the old Soviet void in any near term.