Ryan pursued the theory csl proposed. It works exactly as we said it would. Little if any growth, but increased deficits. All it does is put money into the very wealthiest people's pockets, from which it does little that is useful for the economy.
The theory that there are magic growth beans in lowered taxes always fails (except when taxes are very high indeed), but Republicans are trained not to observe evidence and so they don't ever seem to know what will happen when they do the same silly things over and over.
That's not to say the wealthy paymasters of the GOP don't know. They use the rubes to do what they wish them to. Which is to fill those pockets.