What factors caused websites to win or lose rankings with the July 2021 Core Update?

For my business's website, many keywords for our worst-selling products came up in rankings, many keywords for our best-selling products went way down. We're selling much less in the last few weeks, so we really need to recover.

But I can't figure out what to do. Some competitors are beating us with pages that have low word count, with small numbers of backlinks etc., and I can't identify what it is they have right that we have wrong.

Do any SEOs here know specific things that won or lost after the update?