>>116892359It's because most people sit pretty far away from what's actually happening on the stage, so in the past, the actors had to use loud voices and matter of speech, and use "big" gestures, so that people could more easily make out what's actually happening.
While microphone have helped with the whole sound part, they still tend to have a bit holdover from the old days. It's why theater acting will often sound very differently from movie acting.
But the exaggerated physical acting is still a thing that's very much needed to this day.
Couple that with silly song and dance numbers and it just becomes that extra bit "gay".
