New York — Digital brands looked headed for a reckoning a year ago, with bloated valuations, rising advertising costs and ever more competition.

Then the Covid-19 pandemic hit the US and gave a giant gift to brands that mainly sell directly through the web. With their brick-and-mortar competition shuttered and the virus raging, Americans flocked online and loaded up on home goods, comfy clothes and much more. And this was not just 20-somethings, but pretty much everyone...