You don’t say.
The whole “trickle down” economics concept goes contrary to anything you read in an economics book, actually.
The first introduction you get to Economics in high school contains such postulates as propensity to save (or consume) which directly posits that people will stash away excess of money or invest it for additional personal gain to stash THAT away in its turn. Spending is giving back to the economy; saving isn’t.
Untaxing the rich plays into their propensity to save MORE.