“Trickle down economics” was not invented by conservatives in the 1980s. There was never any such economic theory advocated. The term was always a strawman, popularized by Democrats who opposed the policies of Reagan and free market economists.

▪️Economist Thomas Sowell pointed out years ago that there is no such recorded theory found anywhere in economics. No one actually believed that if you give rich people money it would “trickle down” to the poor, that’s a strawman invented by Democrats.
https://www.hoover.org/sites/default/files/uploads/documents/Sowell_TrickleDown_FINAL.pdf

▪️Those who advocated for lower tax rates did so for two main reasons. One, that the economy will be stronger if people keep more of their money, which will be used to invest in businesses, equipment and innovation instead of frittered away by the government.

▪️Two, lowering tax rates incentivizes working more and/or spending less time & energy sheltering money from taxes. Thus, the net effect will be the same or even more tax revenue. This was JFK’s argument to lower the top rate (which conveniently wasn’t labeled “trickle down.”)

▪️The whole trickle down narrative is a myth. There hasn’t been any such massive decrease in tax percentages paid by the rich. The chart from the CBO clearly shows this (posted in comments). The only notable reduction in taxes has ironically been in the lowest quintile.
https://www.cbo.gov/publication/58781#_idTextAnchor054

▪️In fact, the lowest quintile has a negative tax rate, while the highest quintile has the highest rate by far, even factoring in payroll and excise taxes (chart also posted in comments). In other words, the only trickle down theory in practice is via government taxation sending money to the poor.