Clover is so beneficial that pre-WW2, grass seed mixes almost always explicitly advertised clover content. If you look up 19th or early 20th century catalogs, etc, listings for grass seed will nearly always not only mention that they contain a clover mix, but tout its benefits.
As you note, it was only post-war with the creation of modern herbicides that clover stopped being the norm. There was more or less a DeBeers-style PR campaign to convince people that clover is a “weed” since it can’t survive weed killers.
Clover is so beneficial that pre-WW2, grass seed mixes almost always explicitly advertised clover content. If you look up 19th or early 20th century catalogs, etc, listings for grass seed will nearly always not only mention that they contain a clover mix, but tout its benefits.
As you note, it was only post-war with the creation of modern herbicides that clover stopped being the norm. There was more or less a DeBeers-style PR campaign to convince people that clover is a “weed” since it can’t survive weed killers.