I was under the impression that Beethoven and the other famous composers after him were pretty big and known internationally in a word without internet. I would call that “mainstream”
If you are talking about 20th century, then I would agree with you
Within that small privileged world he was indeed famous across the planet.
Oh?
From The Education of Henry Adams:
""" When his companions insisted on passing two or three afternoons in the week at music-halls, drinking beer, smoking German tobacco, and looking at fat German women knitting, while an orchestra played dull music, Adams went with them for the sake of the company, but with no pretence of enjoyment; and when Mr. Apthorp gently protested that he exaggerated his indifference, for of course he enjoyed Beethoven, Adams replied simply that he loathed Beethoven; and felt a slight surprise when Mr. Apthorp and the others laughed as though they thought it humor. He saw no humor in it. He supposed that, except musicians, every one thought Beethoven a bore, as every one except mathematicians thought mathematics a bore. Sitting thus at his beer-table, mentally impassive, he was one day surprised to notice that his mind followed the movement of a Sinfonie. He could not have been more astonished had he suddenly read a new language. Among the marvels of education, this was the most marvellous. A prison-wall that barred his senses on one great side of life, suddenly fell, of its own accord, without so much as his knowing when it happened. Amid the fumes of coarse tobacco and poor beer, surrounded by the commonest of German Haus-frauen, a new sense burst out like a flower in his life, so superior to the old senses, so bewildering, so astonished at its own existence, that he could not credit it, and watched it as something apart, accidental, and not to be trusted. He slowly came to admit that Beethoven had partly become intelligible to him, but he was the more inclined to think that Beethoven must be much overrated as a musician, to be so easily followed. This could not be called education, for he had never so much as listened to the music. """
The Haus-Frauen had the fortune to be in Berlin. Still I think you underrate the reach of musical culture in general.
Franz Liszt 1811 – 1886 who had early Beatlemania | Swiftie Fever degrees of fervour, dubbed Lisztomania https://en.wikipedia.org/wiki/Lisztomania
Infamously depicted by Roger Daltrey in Ken Russell's movie Lisztomania (1975)
The historical record tends to be overwhelmingly biased towards the interests of the ruling classes, mostly because they were the ones creating the historical record. But taking that into account while reading this, and remembering that people outside of this class were the vast majority of people, I don't see any reason to think he had a massive body of fans outside of this small powerful group.
While that's as aspirational as having the time off and the money and the luck to attend a taylor Swift Concert today, the hoi pollai were indeed familiar through d/loads today and, in past times, through sheet music in beer halls and smaller parlours - music was widespread throughout society beyond just grand concert halls, it was played by "gypsy" trios and quartets who played their own styles and riffed on motifs by "the greats", Beethoven, Mozart, Liszt, etc.
Maybe leave the empty inaccurate quips to other forums?
The term was created while people were creating this genre of music. Classical originally was meant to refer to things from Antique Rome. But, unlike other art forms, like literature and sculpture, no music from Antique Rome survived, no one knew how it sounded.
This kind of created the opportunity to redefine what “classical” meant in music, so a few people decide, centuries ago, that this genre of music would be called “classical” at that time already, not now.