In a simplified manner, yes, it works. Put money towards something and they hire workers to produce it and they buy homes and shop in neighbourhoods and create more work and it 'trickles down' from the initial investment. It doesnt work in practice because people are greedy and its easier to tell the politician you will give them several hundred thousand in speaking fees and a million dollar book deal if they give them several billion with no oversight and the politician signs ont he dotted line.