Well, those folks had to spend a few years planning, take flying lessons, dry run everything a few times, and then pull off the most complicated and coordinated terrorist attack in US history.
The actual bomb planning for the Oklahoma City bombing was less than a year and involved two people. So, seems like the bar was raised quite a bit.
You're giving the 9/11 terrorists far too much credit.
They were supported/financed by the Saudis[0] and America dropping the ball was the only reason they succeeded.
It's not so much a big victory for the terrorists as a big black eye for America and our intelligence agencies.
One of the 9/11 pilots was reported to Federal agencies multiple times[1] and the hijacking still took place.
The actual bomb planning for the Oklahoma City bombing was less than a year and involved two people. So, seems like the bar was raised quite a bit.