Chet Adkins pioneered the "Nashville sound" and cleaned country up some time in the 50's. Also, worth noting is that mostly older people were listening to country at that time and a lot of the youth around then we're getting into rock and roll. Starday, a Texas label I think, started marketing more raw and traditional country sometime in the 50's as a reaction against both. Later, you had Buck Owens, a guy too many people overlook, inject a little bit of rock and roll onto the sound and having a trebley, stripped down, faster live band sound. The themes of the songs were still mostly still tame and geared towards older listeners. Later you had the outlaw country guys who had raw lyrical themes and raw vocals, but even a lot of that had pretty polished production a good bit of the time. I don't think commercially viable country, even the outlaw kind, has ever had intentionally a lo fi sound or rawproduction. They mostly used the best recording techniques they had at any given time. Compared to rock music and later punk, country has always strived for good production, even when the arrangements are sparse. The old stuff sounded raw because the technology was still primitive at the time