I dont remember where I read a historical overview... Malone? The Forgotten Side of Medicine? But:
The issue is not seed oil == bad.
Around the first half of XX century, new industrial and chemical processes allowed the extraction of seed oils in industrial scale, from some plant species which were not used for this purpose before, at least not in industrial scale.
New tech also allowed to extract MORE oil from the same seeds which were used before. sunflower, canola, etc. And this oil extracted under higher mechanical pressure and aided by chemical processes is a different oil.
So, they created new oils, which were not present in tradictional cuisine.
AND, dosing. There is too much seed oil in almost all hiperprocessed foods.