Keynesians imagine that for every dollar they spend it magically multiplies into 2 dollars because the recipient spends it, but they only count the multiplier on the credit side of the ledger and ignore the multiplier on the debit side. Government cannot spend money unless in one way or another it takes it from it's citizens. Whether borrowed, taxed or printed the money is lost from the private sector before it can be spent in the private sector.
This can work on rare occasions when the money spent is an economic investment that would be too difficult for the private sector to undertake, such as and interstate highway system, but little or none of the money is being spent so wisely. Most of it is used to enable people to quit working.