The explanation is that the government massages unemployment figures to make the economy look better than it is. The government has been doing this for decades, under Republicans and Democrats, liberals and conservatives. Unemployment is one of the most widely watched and therefor political numbers; anyone who is in power wants it to look as good as possible. One of the tactics to make the official unemployment rates…
They're just not termed "unemployment", it's labor participation rate or sometimes U-7: https://data.bls.gov/timeseries/LNS11300000
or other flavors: https://www.bls.gov/news.release/empsit.t12.htm
Now I'd agree it is a terrible shame that political and business news media almost completely ignore any introspection in the labor stats of this area.