The basic theory is this:

Fiscal policy combined with Federal Reserve intervention causes inflation (in the short term).

Every time the government and the Fed step off the gas with their policies, the suffocating secular deflation trends of tech growth, globalization, demographics and inequality reinforce the downward trend in inflation and interest rates.

The economy slows, the Fed and Treasury respond at some point with some more intervention.

Rinse, wash, repeat as the secular trends suffocate these government interventions.

If rates were to continue their secular trend eventually toward 0%, the 10-year Treasury bond would earn a 15.5% total return. Not bad for a 1.45%-yielding instrument with the highest credit quality in the world.