It really didn't take a finance expert to appreciate that when interest rates ranged from less than 1% short term to barely 2% at 10 years, interest rates could only go up, 40 year trend or not. And being invested long, for very little gain, was extremely dangerous should rates go up. It has been clear since the 2008 crash that longer bonds had far more downside than upside when rates were so close to zero, so why take the risk?