This happens more than you might expect.
There are several films which became popular staples on television after copyright expired, wasn't renewed, or was improperly registered in the first place (prior to automatic copyright assignment enacted in 1976). It's a Wonderful Life is the canonical example, though there is a long list of other public domain films in the US: <https://en.wikipedia.org/wiki/List_of_films_in_the_public_do...>.
A Wonderful Life fell back into copyright, at least partially, when the musical score was bought by Republic Pictures in 1993.
<https://library.law.uconn.edu/2022/12/08/its-a-wonderful-lif...>
Ted Turner started the Turner Broadcasting System by buying up small local stations with loose licencing arrangement allowing them unlimited reruns of old films and television shows. Shifting to cable distribution for his "superstation" eventually grew into CNN.
(Mentioned in an HN comment about a month ago: <https://news.ycombinator.com/item?id=48038175>.)
I strongly suspect that the popularity of Shakespeare, which grew rapidly through the 19th century, had to do with the demand for popular entertainment combined with the prohibitive cost of contemporary works for many performing companies.
The rise of radio and need to fill airtime likely lead to the popularity of classical music, out of copyright and hence readily available for broadcast, at a time when broadcast rights were at best poorly defined and restricted, if at all. (The concept first appeared in law in 1928, wasn't standardised until 1961, and wasn't globally adopted under the Berne Convention until the 1970s/1980s, or later.)
<https://thelaw.institute/copyright-and-related-rights/evolut...>
<https://en.wikipedia.org/wiki/Berne_Convention#Adoption_and_...>