Thank you for replying, and for satisfying my curiosity.

>> People have thought a computer would never be able to play at that level because chess required some special human ability.

Which people thought that? The luminaries of early AI (before DeepBlue's win) not only thought that computers would beat humans at chess eventually, they thought that it would happen earlier than it did. For example, in 1968 John McCarthy and Donald Michie made a bet with the chess grand master Peter Levy that a program that could beat Levy would exist within ten years of the bet:

In 1968, Levy and artificial intelligence (AI) pioneer John McCarthy were at a party hosted by Donald Michie. McCarthy invited Levy to play a game of chess which Levy won. McCarthy responded that 'you might be able to beat me, but within 10 years there will be a computer program that can beat you.' Levy suggested they bet on it, and Michie agreed to up the ante. Other AI experts signed on later, with the bet total reaching £1,250.[22][23][24][25]

https://en.wikipedia.org/wiki/David_Levy_(chess_player)#Comp...

I think you may be thinking about solving chess, as in mapping the entire chess game tree. I found, in wikipedia, a prediction by Claude Shannon that this wouldn't happen in the lifetime of the universe:

In 1950, Shannon calculated, based on a game tree complexity of 10120 and a computer operating at one megahertz (a big stretch at that time: the UNIVAC 1 introduced in 1951 could perform ~2000 operations per second or 2 kilohertz) that could evaluate a terminal node in 1 microsecond would take 1090 years to make its first move. Solving chess would therefore seem beyond any possible technology at that time.

But that sounds reasonable and entirely different from a computer being able to play chess at grand master level.

Besides that, I do understand your perspective, but I think it's wrong. It's not a big deal that a computer can outcompute a human. We've know that since, I believe even the 19th century, when arithmetic machines could outcompute humans every time. We know that we're no good at carrying out mechanical operations in our heads.

Computer chess was important to early AI researchers, not least among them people like Alan Turing and the aforementioned Jon McCarthy, Donald Michie and Claude Shannon. But those early AI pioneers thought that a computer that could play chess like a human would reveal to us something about the way that humans think, at least when humans play chess. The way that DeepBlue beat Kasparov, and the way that computers generally play better chess than humans, reveals nothing about how humans play chess, let alone think. What's more, computer chess playing relies on very specific algorithms entirely limited to chess and games like chess, so they are not very useful as algorithms, either.

The reason that computer chess is considered such a big deal of course is exactly because those early pioneers considered it a big deal, for the reasons I explain. And those same pioneers were not at all satisfied with the outcome of the project they helped start. Here's John McCarthy again, on the victory of DeepBlue over Kasparov:

In 1965 the Russian mathematician Alexander Kronrod said, "Chess is the Drosophila of artificial intelligence." However, computer chess has developed much as genetics might have if the geneticists had concentrated their efforts starting in 1910 on breeding racing Drosophila. We would have some science, but mainly we would have very fast fruit flies.

http://www-formal.stanford.edu/jmc/newborn/newborn.html

A withering critique. Because computer chess only made sense if it could really tell us something about human chess. That a computer can play chess better than a human tells us nothing at all, and has zero scientific value. So it's a big deal of big old nonsense.