Ethnicity.
In 1972, about 85% of Boomers were white.
In 2016, about 55% of eligible 18 year old voters were white.
Young white people in 2012 still voted about the same way they voted in 1972.
For instance, Romney beat Obama 49%-48% among white women under 30 years of age.
On the other hand, Obama beat Romney by close to 80%-20% among young non-white voters.
Massive LEGAL immigration is destroying Conservative political power.
Since a majority of Republicans still support massive LEGAL immigration, I think violent civil conflict in the USA is inevitable within one or two decades.
You are an optimist.