I mean, easiest example is probably cars. Sure, Elon started Tesla, but they're tiiiiiny compared to other auto manufacturers. They're also doing some things very differently, so it's not quite the "same industry" now. In 1908 there were 253 auto makers, in 1929 only 44, and now there are ~10? So what happened?

There was an initial boom (lower half of the sigmoid curve/hockey stick), followed by lots of competition from startups (because they can compete on method there's some nice profit margins there), followed by brutal competition and diminished profit margins (as best method is adopted and firms sell against each other, things get cheaper), followed by consolidation (because when profit margins are shrinking, next step is consolidation and "belt tightening"), followed by an industry no one wants to touch anymore (because it's run by a bunch of idiot middle managers). If you wait long enough, those idiots eventually miss some major developments and this creates a new opportunity to do things very different (eg Tesla). Or nothing really changes, as in the case of air travel.

Also, history of all kinds of consumer electronics.

Also, how many companies on the fortune 100 50 years ago are still on it? Nothing lasts. If you're lucky and successful, you eventually hit the top of the sigmoid curve.

Also, software (yes, it's true)

What industry does this trend not apply to? What's the argument for "I think an industry being owned by a small number of successful companies represents a signal that a local maximum has NOT been reached (there's tons of opportunity there, just have to unlock it!)"?