Was there ever a time of excitement or 'boom' whereby pieces of music that were hundreds of years old that had never previously been heard before start to get recorded in mass?

Short answer: Yes, it happened. I think we are still going through that excitement.

Let's talk about the curious case of Antonio Vivaldi (1678 - 1741) and his music...

Vivaldi was a composer, teacher and performer in the late part of was later called the "Baroque" period. He composed a lot of music, he did pretty well and his music was known in several countries. And then he died, and nature took its course... Like most music, his went into obscurity. People wanted new music, like they usually do, and during his life it was pretty weird for people to be into oldies, anything older than 10 years was probably not going to make it to public performance. An exception to this: in 1776 a group of noblemen organized The Concerts of Antient Music, and had annual concerts in London from 1776 to 1848. The concerts consisted solely of music composed at least twenty years previous (this was weird, it was mentioned even in newspapers in distant cities, and it was influential in the revival of old music that started in the middle of the 19th century).

So yeah, Vivaldi's music was pretty much not in the picture during the Classical and Romantic periods (that is from his death to the early 20th century). Then the Fire Nation attacked, so to speak, and everything changed.

Friedrich "Fritz" Kreisler (1875 – 1962) was a famous Austrian violinist. He started recording music in the early 20th century (I think around 1915). He composed this concerto (in the late 1920's, I think) and claimed it was by this old Italian master, Vivaldi. This helped bringing Vivlaid's music back from the grave because of the attention. "Fritz" was super famous, and people paid attention to what and how he played.

Copies of a lot of works by Vivaldi were found In the 1920s-30s, so there was "new" old music available, AND an interest to play it because the alpha violinist was playing it (kind of). Vivaldi became mainstream after WWII, and his music has been taught, recorded, played, covered, and whatever else you can think of, ad nauseam to this day.

EVERYBODY has listened to at least a part of this concerto, because everybody and their grandmas have recorded it. Something is not mainstream if a Mariachi band doesn't play it.

The other three concerti that form "the four seasons" set are also played and recorded ad nauseam. Seriously. From electric guitars, to peculiar instruments like the charango, to the venerable accordion. We find women in leather pants dropping the bass in a show with pyrotechnics and dancers.

A currently active composer, Max Richter, rewrote the four seasons and I find it great. A pretty nice example of postmodern classical music, in which you find most of the popular compositional techniques and style from the second half of the 20th century and the early 21st.

Violin students all around the world (try to) play (or butcher) this concerto.

Singers all around the world perform and record some of his killer arias that demand superb vocal technique. Countertenors also sing Vivaldi. Choirs all around the world sing and record his Gloria, some times even with gargantuan choirs and orchestras .

You get the idea, Vivaldi's music came from the grave to be one of the most frequently recorded and performed after WWII, with no end in sight for this trend.