As with many Westerners, when they enter the countries at war within the Middle East, they continue to apply their at-home ways of gullible-behaviour. The security in Israel is there for reasons, that often the inexperienced visitors cannot see. But if knife attackers would had been heading towards the two French visitors, then those same Israeli security forces probably would ensured the visitors safety. Often the unaware need to get a good scare before waking up.