What was Chappell's issue with him?
And the "Bradman provides us only with a small sample" argument goes out the window when you look at his first class average. 230+ games, 95+ average.
Bradman was a bit of a conservative in the 70s and believed that the players should mostly be amateurs. The Chappell brothers were key figures in World Series Cricket. They were on opposite sides of a pay war basically.
And yep nobody can argue that Bradman wasn't special for his time. Those who argue against him basically are arguing that the game has gotten way more professional and that the gap between him and the rest wouldn't be as high in the modern era. Some even argue that Tendulkar or Lara or whoever were as good as Bradman or better. Of course there is no way of proving either side right or wrong, but it's pretty hard to see Bradman as anything other than a legend or a myth he was that far ahead of the rest.
I'd just like to point out that you can pick a chain of players from the 40s to now and look at other players whos careers overlapped and make a case that Bradman would be just as far ahead of modern batsmen as he was ahead of the batsmen of his era.
For example:
Bradman's career overlapped with Compton's career. Compton averaged 50 in tests.
Compton's career overlapped with Sobers' career. Sobers averaged 57 in tests.
Sobers' career overlapped with Gavaskar's career. Gavaskar averaged 51 in tests.
Gavaskar's career overlapped with Border's career. Border averaged 50 in tests.
Border's career overlapped with Tendulkar's career. Tendulkar averaged 54 in tests.
Tendulkar's career overlapped with Cook's career. Cook averages 48 in tests.
By virtue of these overlapped careers, we can clearly see that there is no real escalation in averages. The guys who played in Bradman's era didn't average much differently from the guys who played the era after his. The guys who played half in his era and half in the next didn't find batting significantly more or less challenging after his retirement. The guys who had careers which half overlapped those guys didn't suddenly get better or worse in the latter half of their career. And so on and so forth we go until we get to the modern era where, if anything, batsmen are said to have things easier than they did in the 90s or 80s.
In mathematics we call this a "proof by induction". Knock one domino over and the rest follow. In this case the dominos falling tells us that Bradman would likely have averaged a very similar number, if he played today as a 20-40 year old.