The alternative was investment, in effect spend your way out of recession. I know that sounds counter intuitative but investment leads to the multiplier effect and every £1 spent creates maybe £10 in the economy as it goes down the supply chain. For instance, you invest and decide to say build a house, that means you employ people who receive wages who spend them at the local shop, who makes a profit and invests in more stock from the wholesaler who buys more stock from the supplier who employs more people that means less money spent on welfare to produce the goods, who then earn wages to buy the house.
I know that is very simplistic, but it does create growth.
Neo-liberals assume the market always ends in equilibrium and provides what is needed, but in times of depression or stagnation standard rules have to be suspended and require market intervention. This is where the ideology comes in, the Tories and the Lib Dem Orange Bookists believed in the untrammelled power of the market and that if it was left to its own devices it would return to equilibrium, Keynes thought that not to be the case and that some state intervention was required.
At the moment we are at a stage where austerity has shrunk the market and we have what Keynes called the underemployment equilibrium, this can be shown by the amount of zero hours contracts etc.
There is more, but I am reaching into 30 fucking years ago to recall this and I am a senile old fucker ;))