Walmart, once reviled as a destroyer of small-town Main Streets, played a critical role in keeping the nation fed and clothed during the pandemic, all while generating nearly $560 billion in revenue last year. It did that, like many retailers, by greatly accelerating its push into e-commerce, with digital sales jumping 69% in the last three months of 2020. Now its thousands of stores, many in rural, underserved areas, are vaccinating customers. It’s also taking steps to repair its image as an exploiter of low-wage workers: in February, it announced a broad wage hike.