1 - the CxO class, in the main, have run out of ideas for turning fiduciary capital into physical capital. It's the real productivity increase that pays the vig. Fiduciary instruments are just moving moolah from one pocket to another; no real return.
2 - the Giant Pool of Money continues to grow.
1 plus 2 equals an ever growing tsunami of moolah chasing limited fiduciaries, mostly US Treasuries. Price goes up, coupon is fixed, thus interest rate falls. Treasuries are auctioned, so the best the gummint can do is anticipate demand for an auction. The Almighty Buck remains the global reserve currency, so the Giant Pool fights amongst itself for places at the trough, driving down the interest rate. The Fed's quixotic quest is silly. The suits in the walnut panelled rooms can see what's happening at auction. They must be demented.
The unusual conditions defined by negative interest rates also complicate matters for the Federal Reserve, which has begun to raise short-term rates in the United States, only to see longer-term rates decline. That unexpected development is occurring partly because below-zero rates in European and Japanese bond markets have created greater demand for American bonds, raising their prices and driving down yields, which move in an opposite direction. Negative rates have not been common for very long and their consequences aren't entirely understood.
Sommer has been among the clearer headed mainstream pundits, but still refuses to delve into why real returns continue to decline. An Econ 101 course is in order.