An interesting spin on our current situation.

Borrowed from Quora, wrote by Chris Joosse
The GOP doesn’t have to offer policy ideas people like. It just has to keep enough donor money coming in to finance its own election operations. That’s why they have to keep on pumping the tax cut drill- they’re financed by effectively raiding the treasury on behalf of donors who would otherwise pay much more in taxes. In effect, the GOP gives its donors much more in tax relief than they receive for campaigning purposes. Indirectly, the real donors are future taxpayers- and the GOP is financing today’s operations by raiding the tax kitty to keep themselves flush.

It works the way it does because the GOP are effectively a front operation for a larger, better-organized, private organization called Americans for Prosperity. It is the shadow-political party run by the Koch brothers (and their affiliated donors), and it’s business model isn’t that of appealing to voters. It is in the business of catering to its real clientele, the “donors”- who in turn receive tax forgiveness in exchange for giving a portion of the tax cut on their behalf.

From the donors’ point of view, participation in this scheme is a no-brainer. They see their taxes cut, they give some portion of the tax savings to the GOP, AND they get a class of GOP politicians selling their influence over government policy. That’s a thousand times more influence than they would have by just voting themselves.

Because this scheme is financed on tax cuts, of course the GOP is going to keep on proclaiming false things like “it will trickle down” or “it pays for itself”

In a real way, future taxpayers are paying today’s non-taxpayers to corrupt the GOP on behalf of AFP. Because it’s financed this way, from their point of view, it does “pay for itself”. They sure as hell aren’t paying for it. You are. And the participants in this scheme are making out like bandits, at public expense.

Of course, they’ve gone to the well a lot with this sort of claim, and it doesn’t poll as well as it used to (now that we’ve seen this play out under Reagan, Bush43, and now Trump). So instead, they’re using donor money to buy campaign ads on hot-button issues to distract you:

Republicans have struggled to sell voters on the benefits of the tax cuts despite strong economic growth and the lowest unemployment numbers in 20 years. Instead, candidates and the Congressional Leadership Fund have focused their campaign advertisements on more visceral issues such as crime and immigration. ~[Trump Tax Cut Unlocks Millions for a Republican Election Blitz]

To the question- why do they keep talking about ‘trickle down’ when it’s been proven not to work?

In this scenario, the things they say to you the voter are chaff, a distraction designed to keep you from noticing that the GOP is engaged in a very successful effort to fund their operations on the backs of future taxpayers. So long as that money can be used to buy ads telling you to be afraid of immigrants, muslims, gay people and minorities, they’re pretty confident most voters will be distracted enough to not care.

They also understand that they can count on Democrats to call Republican voters stupid (only an idiot would fall for that line again, right?), and that in turn will motivate republican voters to punish democrats at the ballot box.

They keep on running this play because it keeps on working. They cut taxes, treasury issues bonds to be paid by future taxpayers, the money goes into their pockets today, and they keep pumping their propaganda channels and keep driving Americans’ faith in democracy into the dirt.

Remember, that’s the goal of Americans for Prosperity in the long term- to render the USA into a land that can be ruled from a minority —themselves. [What Is the Far Right’s Endgame? A Society That Suppresses the Majority.] And it’s working. To date, they’ve managed to suppress voter turnout to levels low enough that minorities of the electorate are sufficient to give the GOP (and in turn, themselves) complete control over the United States government.

They do it because it works towards their ends. They have plenty of well-paid political grifters willing to absorb your scorn, particularly if it keeps you hurling your invective in that direction.
Is the weak diffused Dem reaction to all this nonsense part of their well financed shot calling ?
(Sorry if it's a long paste, I don't know the original source ).