'Swing music' is sometimes a term where different people have different ideas of what it means - do you have some examples of films that you're thinking of? - but broadly, the subgenre of swing within jazz came to prominence in the late 1920s with the orchestras of African-American musicians like Fletcher Henderson and Duke Ellington, and in the 1930s, swing rapidly became very popular indeed, with white American musicians like the Dorsey Brothers, Benny Goodman, and Glenn Miller becoming something like household names.

In terms of the music, at a broad level, the same thing happened to swing that happens to every other popular music genre - it got old and then got replaced by other forms. However, with swing in particular there were two big reasons why it declined in popularity quite dramatically after America's entry into World War II. The first was that swing orchestras were strongly affected by members of the orchestra leaving to join the war effort. Other orchestras joined the war effort to put on shows for the troops, and Glenn Miller himself famously went missing in a plane that probably crashed over the British Channel. The other reason was that swing orchestras required large amounts of instrumentalists - they were in an era before consistent electrical amplification, and relied upon the ability of large amounts of people playing loud instruments like saxophones to make large amounts of noise. In the post-war era, the bottom fell out of the swing band market, and because of the sheer expense it takes to run a swing orchestra, having to pay dozens of members, most of the big swing bands collapsed financially.

Additionally, advances in technology and the arrival of new instrumentation played a role; to my mind, you can hear the imminent death of swing in the Benny Goodman track 'Sing Sing Sing (With A Swing)', played live at the Carnegie Hall, which prominently features the drums of Gene Krupa, whose playing style there to modern ears towards the fevered rhythms of rock'n'roll; it's the basic drum kit style of Gene Krupa that's the foundation of rock'n'roll drumming. Similarly, a year after the famous 1938 Carnegie Hall concert I linked to above, Goodman would soon have a guitarist who did something novel in jazz - Charlie Christian played the electric guitar; and an electric guitar going through an amp was able to make just as much noise as a bunch of horns, as any rock'n'roller could tell you.

As to having a genre that everyone can dance to, there is a whole genre of dance music these days, with subgenres like rave and techno and trance. But of course, I think you're wanting to discuss more specific dances with specific moves where people dance together in specific moves - a dance like the Charleston or the Macarena or the Twist. There's certainly still genres with music and dancing along these lines - line dancing to country music, or varieties of Latin genres. However, one of the defining features of young Western people in the 1960s and 1970s was a strong sense of individualism - individuals wanted to go their own way, and to dance to a different drum to everyone else. And so while, for example, disco music had dancing associated with it, it wasn't a collective dance, per se, but instead it was individuals competing to be the greatest dancer in the club.