The performance of small caps is more closely tied to the U.S. economy than large caps are, so with all 50 states in some form of reopening, there is potentially more growth for those companies while simultaneously having a greater defensive posture as they would be more insulated from a COVID-19 outbreak in another country.
We humans like a narrative, a story we can relate to, because it helps us make sense of things, and that makes us feel more comfortable. The fact that the stock market was up about 19% over the previous four months, based on very little improving fundamentals, set us up for a tumble.