Perhaps I'm having a Mandela Effect moment, but hasn't "trickle down" been debunked before this study...repeatedly? Not just "no shit", but actual studies and stuff? Regardless, Will Rogers is credited with the phrase "trickle down" to refer to supply-side economics, so it has gone on longer than 50 years. Mr. Rogers also did not mean the turn of phrase to be complimentary.
Regardless, it's still the central dogma of the politics of a large part of population.