This is wrong on many levels. There isn’t much effort put into preventing those kind of attacks outside of really dense venues like stadiums.

Train and subway stations rarely have more than one or two armed officers if they have any at all.

Train tracks have shockingly little protection to prevent timed derailment sabotage. Buildings have little protection from being surrounded by accelerants and set on fire, etc.

There is a strange subset of things terrorists seem to want to do and society doesn’t do much to prevent the rest.