Central banks hold gold in their reserves alongside dollars and other currencies. Many have been adding to it, partly to rely less on any one currency.
They buy in large amounts and rarely react to the news of the day. That gives gold a slow, steady support that does not show up in any single headline, and it can help explain why gold holds up when the textbook says it should fall.
Their buying tends to be reported with a delay, so it rarely explains a move on a given day. It matters more over months and years.