But that's still surprising performance, because the S&P generates income and pays dividends. Its increase reflects (at least, is supposed to!) expectations of future higher income. Gold doesn't even bear interest....
The S&P doesn't really pay much in the way of dividends does it? Last time I checked it was order-of-magnitude 1% which is a bit of a joke figure.
Anyway, there isn't a lot of evidence that the value of gold is going up. It seems to just be keeping pace with the M2. Both doubled-and-a-bit since 2010 (working in USD).
Gold is commonly seen as a hedge against inflation and a decently stable non-currency store of value. With many countries having/being perceived to have high inflation during this time, the price of gold is bound to rise as well. Pretty much any economic or sociopolitical tremor will bounce up the price of the gold at least temporarily.
For comparison: S&P500 grew about the same during that period (more than 100% from Jan 2019, about 70 from Dec 2019), so the higher price of gold did not outperform the growth of the general (financial) economy.