As with almost all markets Those who control are longs and...

As with almost all markets
Those who control are longs and shorts.

The USD is the reserve currency.
Gold is seen as an alternate currency.
As such the value must be controlled by central banks. In particular the FED.

I imagine that within limits they let the market run.
When it is decided that the market is trading outside these limits they step in.
Buying or selling when required.

Cheers