Donald Trump is totally correct that nuclear war would be a terminable event and that nothing is more important than restoring a cooperative and mutually respectful relationship between the US and Russia.
The problem is that the military/security complex sees it differently. After 70 years of entrenchment the military/security complex is an independent political force. President Eisenhower warned the American people about this likely outcome in 1961 to no avail. From the standpoint of the military/security complex, the problem of normalizing relations with Russia is that it downgrades the “Russian threat” that is so essential to the $1,000 billion annual budget of the military/security complex and the power that such a massive budget conveys. Only 16 countries in the world out of 195 countries have a GDP greater than $1,000 billion. The military/security complex is large enough to be a member of the G-20 and to have its own currency and military.