From the 30s to 50s, speeds of most popular songs slowed from ~40 to ~30 bars/minute.
When music was played at "Society tempo" of ~40 bars/minute, people "crushed" in packed dance halls to do SOCIAL FOXTROT. On the quicker steps, they literally "Society bounced" & partially closed their feet in chasses. Rent the video "The English Patient" set during WW2 to see Ralph Fiennes & Kristin Scott Thomas bouncing so. In "Top Hat" (1935), before Fred Astaire & Ginger Rogers did their choreography to "Cheek to Cheek", they social foxtrotted during the singing part.
If there was more space, Americans did the Peabody (comparable to the Quickstep), which at that time people considered a fast foxtrot. They walked in circles alot.
The harmony between speed & steps came in the 50s when tastes for song tempos slowed to ~30 bars per minute, like Frank Sinatra's "Witchcraft", "Come Fly With Me", & "The Lady Is A Tramp". With decelerating tempos, the social foxtrot got smoother; Arthur Murray standardized (SSQQ / SQQ) and codified the steps to what we call the Bronze American syllabus (10-12 figures).
By the late 50s when music slowed to less than 25 bars/minute, ballroom dancing was eclipsed by the Twist & other non-couple dances. Many lovers who didn't learn ballroom held each other to rock to and fro.
In the 70s, people learned to ballroom in discos by doing the hustle. At the same time, they did salsa-like steps ("Disco Slow") to either slow tunes ("Touch Me In The Morning", "All By Myself"), or slow disco intros ("Love Hangover", "MacArthur Park", "Enough Is Enough"). Such salsa-like steps are still undergoing systemization to form the Nightclub Two-step syllabus.