Since the 1990s central banks have been given the target of keeping inflation low. 2% has been the goal. But in practice as this diagram shows, the trend was already strongly downward before central banks were given this goal. Achieving it was not a problem as a result.
It’s also important to note interest rate trends. These have been steadily downward over hundreds of years. There’s no reason to think that central bank control of interest rates has had anything to do with this over the last couple of decades.
He uses real interest rates in the second paragraph, not nominal.
There are good reasons to think inflation and interest rates move in line with each other. If inflation is high interest rates need to be higher to pay real rates of return. The fact that the two move together is then unsurprising. But also reassuring, because they do.