This seems like one of those strawman political football arguments.
Also, the methodology here is a bit flawed. I think that economic data that cherry picks the start of the covid-19 pandemic is deeply flawed. 2020 will always be known as an economic outlier. It's like selecting 2008, or September 2001. These are data points that should be eliminated from your data set - not highlighted in your conclusions.
Seems like just another anti-billionaire political hit piece, frankly. No real substance.
Also, a nitpick - the STUDY didn't take 20 years. The DATA was from a 20 year period. The title builds the study up to imply far more effort than was actually expended.