I don't think this is quite right. The problem is that the TSA's incentives are all screwed up. Any time some idiot manages to sneak a weapon onto an airplane, the TSA leadership gets attacked for it, whether or not they could have reasonable predicted it. But there's no penalty for instituting a new policy that is massively inconvenient (or embarrassing) for travelers but doesn't actually make people safer. So there's a one-way ratchet effect, where they keep adding new layers of security theater but never retire old ones. And because they're insulated from political accountability, there's nothing travelers can do to push back.
Public opinion is rarely coherent or rational. Most voters think Congress spends too much, but if you poll individual big-ticket spending items, almost all of them are popular. Similarly, I imagine many of the specific "security theater" measures wouldn't poll very well, but "more secure airports" is overwhelmingly popular, and that's the level of abstraction at which the TSA's mission is set.
Public opinion is rarely coherent or rational. Most voters think Congress spends too much, but if you poll individual big-ticket spending items, almost all of them are popular. Similarly, I imagine many of the specific "security theater" measures wouldn't poll very well, but "more secure airports" is overwhelmingly popular, and that's the level of abstraction at which the TSA's mission is set.