Scientists Hoped Summer Temperatures Would Tamp Down Covid-19 Cases. What Happened?

When the pandemic first began, many thought that the hot summer months would keep the virus from being able to effectively spread. However, this hypothesis was inaccurate and the United States is facing a second surge that has surpassed the first. Why is this?

 

https://www.wsj.com/articles/scientists-hoped-summer-temperatures-would-tamp-down-covid-19-cases-what-happened-11594632601?mod=hp_lead_pos6