How old are you? I think a lot of younger folks don't fully adjust for important factors: plane hijackings used to be much more common, 9/11 was committed by the second group of Islamic terrorists who tried to blow up the World Trade Center, and 9/11 was the third major terrorist attack by Al-Qaeda in a 4 year span. It's easy now to say that it was a crazy worst-case scenario, but that was not at all obvious then; for all we knew, securing cockpits might have been impractical, and we'd just have to prepare the Air Force to shoot down a couple hijacked flights every decade.
There were real excesses, and I ultimately agree with you that many of them were predictable in advance, but there was no feasible version of a response that did not go at least a little into crazyland. It was a crazy time.
"Real excesses" is a bit of an understatement. There is the security theater instituted by the TSA, the militarization of police, normalized Islamophobia, mass surveillance of U.S. citizens, torture as an official military policy, indefinite detention of "unlawful combatants", a trillion dollars spent destroying Iraq and Afghanistan, a million killed and many more made refugees. The rise of ISIS and the refugee crises in Europe can be traced back to the War on Terror. The Middle East should not be the punching bag for America to take out its "crazy" feelings (where "craziness" appears to be a polite way of saying "bloodlust").
It was a crazy time, not in the danger from hijackings but the enormous amount of fear and cowardice America built up within itself. It was crazy because of the mass hysteria not the violence. Take this example: 1.2 million Americans died from Covid. 3000 americans died in the twin towers attack. That's 0.25% of the number that died from covid. However we gave up considerably more liberty to defend against the hijackers than we did the virus. It was a very unusual incident but the response wasn't warranted. I mean like 1/3 of the people who died in the twin towers, about 1000 people a year, die from being hit by trains, but you don't see anyone demanding we give up constitutional rights, or do literally anything at all to change that.
> younger folks don't fully adjust for important factors: plane hijackings used to be much more common
https://en.wikipedia.org/wiki/List_of_aircraft_hijackings
(I can not say how comprehensive that wikipedia list is).
There's more in the 70s and 80s than I was expecting (having lived through the 80s), but given how many flights there are, hijackings have been and are exceedingly rare; and most of these are not even US flights. These are "driving is orders of magnitude more dangerous than flying" and "10x a very small number is still a very small number" numbers.
https://businesstats.com/global-air-traffic-number-of-flight...
https://easbcn.com/en/how-many-planes-fly-per-day-around-the...
https://www.iea.org/data-and-statistics/charts/world-air-pas...
These numbers only serve to re-enforce that the response of giving up liberty for (the feeling of) security due to terrorist action in the US was probably outsized. General population awareness in general was probably more of a deterrent after 9/11 than any of the first order 9/11 response actions, especially considering that the US gave countries in the middle east further reason to hate Americans and US foreign policy after 9/11. Obviously, terrorist attacks get a lot of air time and column inches, which feeds the perception of the risk.