I'm surprised you mention us not having recordings of the older times being why we thought people spoke eloquently. Even in old recorded audio and video, like old TV, it feels to me like people speak much more eloquently.
Prepared speeches don't really count; they're basically reading written prose. I'd be interested to hear actual conversations from Victorian times. I wonder if they are anything like how we write them in TV shows and movies.
Well, we do have recordings from that period, but it would be as out there as having a finetuned AI of your own writings these days so I don't know how natural it would have been.
Also, apparently TR used the manuscript much less than most speakers, delivering much of the actual wording impromptu and the general structure from the script, so he was actually pretty fluent off the cuff.
