Not all the inflation was intentional or controlled.
Two linked aspects that were were:
The Nixon admin believed that lower federal interest rates would help stimulate the economy by making it easier for businesses to obtain loans and invest in creating jobs. He replaced the Fed chair with an ally who would keep rates low, even when it started to lead to higher inflation. The philosophy was it was more important to control unemployment than inflation.
There was a belief that the rising inflation was itself stimulating to the economy - if money is devaluing then people with cash will want to quickly spend/invest it, which is generally thought of as being good for the economy. But it didn’t have the desired effect, at least fast enough, to bring down unemployment to the levels required and prices inflated faster than wages.
You’ll probably note the basics of these ideas are still present in a lot of economic measures taken since the Great Recession, we haven’t had major inflation during that time though, possibly because the economy is now structured so the vast majority of the cash goes very quickly to a very small number of very wealthy people, so it’s not circulating among most of the population.