See <a href="https://ethw.org/Picturephone" rel="nofollow">https://ethw.org/Picturephone</a> which showed that for all their genius, Bell Labs couldn’t make a consumer product to save their lives. AT&T was able to improve the internal operations of the Bell System in that time period but the last product AT&T made before the breakup that made a difference for customers was the single-slot coin phone.