The two main pillars of any economy are interest rates and money in circulation. Central banks have the power to manipulate both independently; this allows them to work as alchemists and speed up or slow down the economy according to their needs.
The main problem is that a good economy for a central banker is like heroin for a drug addict.
This interest in the economy doing well has meant that the two main levers of any economy: interest rates and money in circulation have fallen in the long term. It is true that in the short term, there are certain moments in which they try to put the brakes on by raising rates (or decreasing the money in circulation, QT), but as we see below, in the long term, both interest rates and the value of money tends to 0.