Except that there were relatively few hijackings prior to the TSA. Airport security of some form, sure, but it was wildly different than the TSA. I've had an infuriatingly large number of nonsensical encounters with the TSA and would love to see that agency torn down and replaced. If not both, then just torn down.
Arguably the two main deterrents from further hijackings in the US have absolutely nothing to do with the TSA: prior to 9/11, complying with hijackers was usually considered the "right" response. Also prior to 9/11, few if any airliners had secure cockpit doors.