In 1969 after repeated police raids the gay and transvestite customers of the Stonewall Pub in New York resisted arrest and spontaneously protested on the streets. After a protest lasting a few days they won, the police were forced to back off and Gay Pride began.
The music played in the gay nightclubs that followed was Disco, which the gay and gay friendly community danced to.
"Disco Demolition Night was an ill-fated baseball promotion on July 12, 1979 at Comiskey Park in Chicago, Illinois." As a publicity stunt to sell tickets they blew up a crate full of disco records. It was a homophobic reaction against the gay nightclubs and the disco music they played.
In the 1970's and 80's short shorts and speedos were just what you wore for soccer, running and swimming. Short shorts were just called shorts as nobody except pensioners (with old army surplus shorts) wore long shorts. In the UK we didn't know about board shorts as surfers wore wet suits.
In the late 1980's there was a change in fashion from wearing brief underwear to wearing boxer shorts, the boxer shorts were actually longer than the soccer shorts worn over them which looked dreadful so men and boys started looking for shorts to wear that were longer than their boxers.
At first those who continued to wear briefs were considered unfashionable but gradually swim briefs and short shorts started to be considered as inappropriate and then gay.
In 2003 this advert came out:
https://www.youtube.com/watch?v=lbnkhqzp4l8
The age of wearing the same big baggy shorts for everything had arrived.