Well, hopefully not depression.
AIUI, the idea is to constrain the money supply until the quantity of goods and services around has grown to match the amount of money created, without too much disruption.
The excess money printing happened because the government wouldn't expand goods and services demand after the 2008 crash. We always knew it was less useful and had a worse after-party hangover than doing the right thing, but the government wasn't doing the right thing, and it was the only thing a central banker could do to help people at the time. It was the right call at the time, in the circumstances. But now we've got the hangover.