Well said! History is a valiant teacher especially when you can interpret it right.When most "formal" entertainment was on the stage (18th & 19th centuries) Opera was the most expensive, expansive, extravagant of staged works - huge casts, singing, dancing, fabulous sets, special effects, costuming, etc. Using the term "Opera" when applied to visual media such as TV and film reflects that expansive, extravagant production style. A John Ford style western (with the incredible western vistas, and huge battle scenes) was often referred to as a "Horse Opera," just as a long form continuing daytime TV series whose advertisers marketed to female homemakers (selling them dish soap, washing machine detergents, etc.) were called "Soap Operas." This was later applied to Star Wars style film making (as Lucas said, "It's a Western set in outer space"), so by extension those huge budget, extravagant outer space films became "Space Operas."
See? History can be fun and interesting!
As a sound guy I always loved the story of John Dennis. He was an unsuccessful playwright in the early 18th century. Back then, when a thunder sound effect was needed, they would use a cart with uneven wheels filled with rocks (or something similar) and roll it across the stage (behind the sets, of course) and use a lever to pick it up and drop it to create thunder sounds, which required a lot of space. In the very small theater where John Dennis presented one of his plays there was no room for these large sound effects machines. Although it is unclear if he used a version of the mustard bowl technique (a huge stone bowl for grinding mustard seeds was placed on a large box and rough cannon balls were rolled around inside), or hanging a very large extruded sheet of metal (the classic thunder sheet) as a solution to this problem, the idea was quickly picked up by other theatrical producers after his play failed. When Dennis attended one of these plays and noticed they were using his idea he supposedly shouted "DAMN!!! They stole my thunder!"