1: MAD doesn't really work anymore because of the advent of hypersonic cruise missiles and the likes of russia's Burevestnik/Skyfall. There's probably not going to be a 1980s scenario of two sides launching all out against each other and having a few minutes to contemplate the end.

2: Tactical (not strategic) nuclear weapons are very likely to be used on the battlefield in the next major conflict involving the superpowers. The most plausible pathway to a nuclear armageddon is if the number and yield of these tactical weapons keeps escalating until one side finally has enough and launches a strategic strike.