Originally Posted by
Bloble
Well, that is a valid question, and I'll try to answer it as succinctly as possible.
First, one of the reasons Archie had no trouble with the ward is that he never actually experienced it. While Moriah and the Scribe were exploring tombs, our Magus was sitting under an umbrella and sipping on tea like a boss. He merely saw the symptoms, which were really just an irrational urge to avoid the area being warded. From there, he deduced that they'd fallen into a trap, and guessed correctly. It's not unusual. Similar wards exist and are commonly used even in modern times. Now, breaking the effect of the ward is much easier than getting past the ward itself, sort of like how it's theoretically simple to break out of illusions in Naruto (simply cycle chakra through your system) but much harder to actually create them. It's even easier in this case to break the effect as an outside observer, hence why Archie was able to free the two so easily.
Second, the reason they were affected in the first place is pretty much because they weren't expecting it, coupled with the ancient magic being awesome enough to get past any passive shielding most magi have against such a trap. For reference, look at how Caster remotely controls Shirou in UBW despite him having magic resistance as a magus. This is a similar phenomenon. If they had active shielding and were expecting it, even the age of the trap wouldn't be enough to let it work, but in this case it did because they were caught unaware.
And, of course, the passive ward is just as you guessed, merely the first layer. It would have been less than effective a few thousand years ago, but here even that small cautionary measure is enough to almost divert the team from their goal. You can think of it as the difference between Ancient Egypt's magi and a modern magus.
EDIT: TL;DR, Ancient Egyptian magi are even more ancient than that old grannie Caster and can pull off some hax shit. Scribe got cocky, and Archie made a lucky guess.