If tax cuts for the rich improve the economy, why is the economy in horrible shape?

It is called trickle down economics; the rich get money, and it trickles down to the poor. Hoover tried this theory during the Great Depression and failed. People now turn to Keynesian economics, which, I believe is better, at least short term, if not long term. Besides, the rich tend to be greedy, so this explains the trickle down theory problem.