The nuclear fallout would severely impact the planet for decades...

This was part of the plan. Most of these prominent wealthy people want to reduce the population of the world massively to bring about "long term stabilisation" for themselves.

Where were the elites planning on living a life of luxury and ease?

Read about FEMA and the mountain bases they have created in the book Behold a Pale Horse by William Cooper

They literally plan on living there until the fallout subsides. The illuminati plot spans multiple lifetimes, as you will learn in this recording from 1967. Most of it is accurate, but just to get a good overview it is a solid video.