Very roughly, you had liberalism until that crashed in the 1930 with the Great Depression.
Capitalism was rebooted with social liberalism to include welfare, education, healthcare. In the seventies that ran aground in stagflation. Rich people didn't like investing anymore as the profits weren't big enough to their liking with all that welfare. Then came the oil crisis and that killed it completely.
The system was rebooted again with a tweaked form of liberalism, so that's now neoliberalism. It repeats all the mistakes of that past, slowly salami slices welfare and healthcare away, chips away at all the safeguards and then crashes again in 2008 with financial crisis.
After that, the system was basically resuscitated, pumped full of money to keep it going and now we see how long it lasts before something really bad happens. Welfare, education and healthcare are turning into dust for most people so something going to give.
Lyndon Johnson thought he could knock the Communists out of Vietnam with one massive push. That plan failed and LBJ was stuck with a giant war. He didn't want to raise taxes so he printed money. Nixon ran as a pro-peace/anti-inflation candidate, then doubled down on both of LBJ's worst policies.
In the middle of all this, the Arabs tripled the price of oil, which really skyrocketed inflation.
Carter managed to slow inflation by hiring a guy named Paul Volker, but Jimmy was kicked out before his policy began to kick in.
Reagan kept Volker, but Ronnie cut taxes without cutting spending. He gave the rich a big boost, plus he let the S&L banks give out loans to anyone who could walk in the door. When the banks failed, the taxpayer had to bail them out.
In 1968, middle class was still defined as one income supporting a family of four. In those days $1 million was considered a vast fortune.
By the time Bush Sr. left, 'middle class' was two jobs to support a US home, and $1 million was what a rich guy paid for a party.