In general, Congress, the president, and the Federal Reserve tend to create economic policy through a mixture of their own ideals and realpolitik.
You could say the Great Depression compelled then president Franklin D. Roosevelt and Congress to embrace robust Keynesian economics. The branches worked together to pass a set of laws in which the government would forcefully intervene in the economy. They created jobs programs, established unemployment benefits, and imposed restrictions on banks.
Herbert Hoover, the president before Roosevelt, was a conservative. Yet he, too, tried to combat the ills of the Great Depression with Keynesian economics. Federal spending rose almost 50 percent during Hoover’s time in office. However, it appears as if Hoover’s conservative ideals obstructed him from embracing Keynesian economics as vigorously as Roosevelt.
You might also think about how all three recent presidents have embraced a form of Keynesian economics.
For most of his presidency, George W. Bush embraced laissez-faire economics. He pushed policies that let Wall Street and the market operate with little restrictions. However, when big banks and financial institutions began failing in 2008, Bush pivoted to Keynesian economics. Bush’s government intervened in the economy with billions of dollars.
When Barack Obama became president in 2009, he immediately espoused Keynesian economics with a stimulus package of around $800 billion. Yet some economists argued that Obama’s government should have spent more money, like a trillion dollars.
Recently, president Donald Trump, who holds aggressively laissez-faire policies, pivoted to Keynesian economics. He and Congress passed a $2.2 trillion relief bill to try and offset the financial hardships caused by COVID-19.