It is unclear why the US Federal Reserve has allowed this to occur.
My WAG is that is a side effect of the Fed's unwinding of over $500 billion in central bank "dollar swaps" undertaken about a year ago. That was blantant attempt to push the dollar higher, that many financial professionals clearly misunderstood. The reversal of that policy has caused the dollar to come tumbling back to earth.
Anyway those extra dollars from foreign countries probably at first migrated to US banks, or US bank branches, and became part of M3.
However the key point is that does this portend bad news for the economy is - generally so, but the effects of recents inflationary actiosn by the Fed, ECB, and IMF will probably reverse that decline before long.
It's already over, now it's just a matter of adjusting.