It doesn't. Biggest political fraud ever perpetrated. The past five years provide clear and direct evidence of that.
But it can work, no worries, granted it requires benevolence among the elite, and that is what is lacking in society.
Any system of economics and governance can work perfectly well if operated benevolently. The problem does not lie in the methodologies but rather the goal. Our goal is to gain more wealth, that is not a goal of any value. The goal should be to live better and enjoy life as well as assure that future generations have a solid foundation, we aren't doing well at that, in fact, we're kinda melting down.
Imagine that we are closing uranium based nuclear plants and reverting back to gas rather than progressing to Thorium, do you believe that is wise? Failing to progress in the natural order of time and even regressing? Does any great advance ever come from stepping back?
Time is advancing, the population is advancing, our infrastructure needs to advance, yet it's not happening because the market is afraid of change and values, it has no vision, that is why it is the market living as parasites off producers and consumers taking their cut every time the money changes hands (the product is irrelevant).
You are correct though, as it has been operated, trickle down is a fraud, a lie, because the benevolence required does not exist in the market, and we hand over our economy to the market like we can trust it to do the right thing; Greenspan finally did figure out that was incorrect. He was so smitten with Ayn Rand's imaginary crap that he forgot to see the reality that people are selfish, stupid, and destructive. It really broke him to admit it in front of congress.
The problem is, we have been feeding that system since the 80s, so that is where all the money is like it or not. So, the options are to just seize the money, leave everyone with no more than $10MM and whatever hard assets they own, Federalize all the gold again, and start over; or we can incentivize those that have accumulated the wealth to insert it back here. Make it attractive to spend the money with tax bonus on it.
"Off shoring" money is of limited value, because money is worthless until you spend it on a tangible product. As many .com millionaire with a Cayman account soon found out, "hey, I have to pay taxes on this money in order to spend it."
It's not that difficult to beat to taxation rates anywhere else it's worthwhile to spend money. Heck, with the tax bonus incentive it actually makes sense to bring manufacturing back to the US, especially hydrogen energy industry production. At a three to one credit you can buy a piece of infrastructure and be able to have a billion tax exempt dollars. I'm all for leading the rich with carrots. Spend a billion on H2 Infrastructure and you can have $3 billion tax exempt, not to mention the earnings from the infrastructure.