So the Knights Templar around the 14th century have a series of bad losses in the Holy Land, the nobles don't like them, they own all sorts of money and land, there's a lot of mystery surrounding them.
The inquisition start to arrest them and extract confessions of heresy and debauchery via torture. In 1307 apparently there were as many as 15,000 arrested in France and thrown in the dungeons.
Here's my question: You're a holy warrior order. You own everyone's money and land. Theoretically you are in a vaguely sustainable position. A bunch of people, who gave you their money and land for keeping safe, turn against you. Then this group of theatrical guys thumping bibles start arresting your guys, on bullshit charges, spreading propaganda, and torturing your men. Why in the world did the Templar's Grand Master not say: "Ok, that's cute. I have the gold. I have the land. More importantly, I have the swords. You're fucking dead, mate." and march an army into the inquisitorial holdings and start killing bitches? It doesn't make sense to me that they even allowed this stuff to happen to them, seemingly without much of a fight. This seems like a reasonable thing to do.
Anyone able to shed some light on this for me?
If that were the narrative, what you say as a reaction would make sense. However, you've got virtually every part of the story incorrect.
The entire capo of the Templars in France, including Grand Master Jacques de Molay, were arrested by surprise by the bailiffs and seneschals of the King of France, Philip IV. IF I had to put it in terms like you have:
"Ok, that's cute. I have the gold. I have the land. More importantly, I have the swords. You're fucking dead, mate."
Then I would refer you to the equally fictional end of Godfather where Michael has the heads of competing mafia Dons killed at once. I hate this comparison because the suggestions of equivalency of power, and the absence of a third mediating power, are wrong for describing the relationship of Philip to the Templars. But it makes do for the effect of complete and utter decapitation of the order in France.
Philip IV (The Fair), and in particular his ministers Guillaume de Nogaret and Guillaume de Plaisians, waged a significant propaganda campaign against the Templars before this, seeking their dissolution and arrest by the Church. However neither the papacy nor any Papal inquisition were involved in the arrest; in fact, Pope Clement V declaimed Philip's assumption of jurisdiction in arresting Templars for heresy. The arrests and torture were conducted by secular authority:
thanks to the indulgence of the inquisitor of France and royal devotee, Guillaume de Paris, the jurisdiction of the Church acted under the king’s direct control, in fact if not in law. ^1
It was only a few years before this that Philip had attempted to declare the previous pope Boniface VIII a heretic himself which had lead to years of running crisis between papacy and king.
The whole episode is reflective of Philip's seeming desire to assume authority of the Church himself after years of conflict over the papal role in the rule of France.
^1 Julien Théry, A Heresy of State: Philip the Fair, the Trial of the “Perfidious Templars,” and the Pontificalization of the French Monarchy, Journal of Medieval Religious Cultures, Vol. 39, No. 2 (2013), pp. 117-148
You're missing one essential fact: the Inquisition was not behind the arrest of the Templars. It was the King of France, Phillip IV. Phillip IV would later go on to arrest had previously ordered the arrest of the Pope (Boniface VIII). He certainly did not have any fear whatsoever of the Templar order. By 1307, the Templar order was far less wealthy and powerful than it had been at its peak. The time of overwhelming European interest in crusades for the Holy Land had largely passed. The Templars had been steadily losing ground for decades and had been driven out of their most important fortresses and holdings in the Holy Land. With those losses came a great decrease in the actual fighting capacity of the Templars. Most of their European bases weren't castles full of standing troops, but centers of bureaucratic administration. Philip IV's order for the arrest of the Templars was given out to royal agents in secret and caught the Templars completely by surprise. Being spread out across France and the rest of Europe, they had no time to effectively organize for any sort of armed resistance. Even if they had, it's extremely doubtful that they could have fielded a force capable of challenging the army that the King of France could have put together much more quickly.