>>but it might be the second foremost reason why Cortez was able to conquer them - the first being Montezuma’s reticence to slaughter them in the jungle when he first heard of them and his subsequent religious obsession with the white conquistadors, until it was too late and they were well established.

Montezuma was never in a position to slaughter the conquistadors in the jungle. The Tlaxcalans (a rival state to the mexica) engaged the conquistadors in a series of brutal skirmishes (most with the advantage of surprise) on their home turf but failed to make any real progress. Its very clear that the attacking Tlaxcalan warriors suffered horrendous casualties when they engaged the castillans in close quarters combat due to the superior steel weapons(mostly swords) of the latter. Since the Tlaxcalans vigorously defended their independence its hard to argue the Mexica could have done any better fighting at a distance that would have stretched their supply lines.

As for his supposed religious obsession, its unclear and isn't necessary to explain his actions. There is certainly no evidence that Montezuma was confused or acting irrationally; he repeatedly tried to deter the conquistadors from coming and made attempts to play them off against the Tlaxcalans.