Can I take a ride in your time machine please?
nothing about 'seeing' anything. there are indeed facts known about the time period, tennis was not international at the time, and it was nearly as popular in that time as it was a century later
there is no plausible way you could argue that Renshaw had extreme competition of the time, hell he was mostly only playing other Englishmen
the circumstances are the circumstances and I would not entirely use them to hold anything against his records, BUT when directly comparing two great grass players of very different Eras things like this are important to take note of. if I was arguing Renshaw was less talented than Federer then it would be something you'd need a time machine for, but just arguing that his accomplisments were easier at that time than they would be today is something you can generally assume