I don't have a link, but I heard NPR quote/paraphase the CDC director Rochelle Walensky, who said that they needed to moderate the guidance to account for what people would tolerate -- give people a medicine they'd actually take -- and that the 5-day guidance struck a balance between the data that transmission was often reduced after 5 days (followed by masking) and that that was better than businesses presumably ignoring the quarantine period altogether.

I haven't seen anything where they directly said "businesses asked, so we did it", but I have heard state governors interviewed saying they asked (for business/healthcare continuity) and in their view the federal gov helped them out.

I don't think there's a "we ignored our judgement and just did what people asked" smoking gun to find though. It would have been nice if they required a negative antigen test before returning, though.