Sorry but you seems to miss a basic point : one must take political promises carefully.
The armagnac just wanted support to fight their civil war. There are promises which are meant never to be held. Such as : "Finally we'll give you money and that's still too much."
But you don't really take them carefully, you're assuming something, that really honestly I just didn't found in contemporary sources.
(Admittedly, I didn't consult the actual articles of peace, but that would take quite a time to have them)
The main problem I've with "It was never meant to be" :
- That Thomas Clarence came, personally, to help Armagnacs besieged in Bourges.
- That some land was actually gave to Clarance in Guyenne (that is generally described to be let alone to itself, not defended) and Armagnacs/Berry described by Bourguignon as "traitors"
- That Armagnacs before the truce were in need of help, as being under heavy attack (not "just some support").
Giving their regular lack of financial ressources the "just some money" is itself something far from insignificant (as sending hostages later), but weren't much in a position to be that "smart" at this point.
The Duke of Burgundy (again, the "power behind the throne" in 1412) didn't just made peace with Berry out of kindness, but because English help and increased presence was actually a threat to him.
Giving what happened with Bourguignons after 1415, when they became once again the dominant force in Northern France, I think we can say at least one of the factions in presence was willing to make huge concessions (and Armagnacs not being exactly little saints there, I don't see why they wouldn't have).
I'll stress on this last point a bit more : being willing to give up part of the kingdoms didn't mean you were joyous or not willing to get them back later. That's basically what happened IOTL and what would happen ITTL (given that both factions based themselves on reject of English at this moment).
Without the truce of 1412 (that is, considering how Burgundy changed his mind in 1413, quite butterfliable), it's quite probable that other parts would have been gaven, as the process already began.
Basically, Burgundy takes Bourges, and by holding Berry, beheads the Armagnac faction (that never had a clear leader to begin with).
Giving that Bernard of Armagnac is the "by default" leader (depsite what the name of the faction seems to imply), that he lost an important part of the faction holdings, he's not going to be smart about it.
If renouncing to coastal Guyenne (something that is by mid-year, already done) and Perigord (critically when it gives an actual buffer region between his holdings and advancing Valois-Burgundy alliance) would be the price (even if temporary) he'd pay it.
The same way territorial renounciations were made later by France, while in a definitely better shape (by Charles VIII for exemple) in a political purpose.
I understand your caution there (after all the subject was heavily politicized, even and critically contemporary to events), but frankly, I didn't found anything that would support it.
France was 4 to 5 times as populated as England. Even weakened by civil war, Henry V's campaign could and even should have ended by a disaster,
France was so strong nobody managed to stop Thomas' campaign in France in 1412 (Boulonnais to Bordeaux) at all.
Both sides didn't even think about really fighting him (the most that was made was put new garrisons to prevent Thomas reaching further regions, while Boulonnais was in flames) but rivalized with promises, Bourguignons making arrengement firsts, then Armagnacs doubling not only on money but with territories they controlled.
had the french command not been so stupid.
And again which french command? The whole army was so divided that you could have made a patchwork out of it.
Bourguignons troops were present against the duke's wishes; Jean II le Meingre technically commanded the army but technically covers it well; Bernard of Armagnac was Constable but disregarded("All the lords wanted to be in the vanguard, against the opinion of the constable and the experienced knights."); Charles d'Albret being as well with some theorical power, but not enough support to do anything with it; and all the rest likewise.
They failed to lead an army the same way they failed to pursue negociation : because no one really commanded it, because they were divided up to an absurd point.
If something, it's another demonstration of the civil war weakened France :
the campaign of Henry V had few chances to going really bad, mostly because the 1412's prooved that there was no big resistance to meet, and because Henry could count on an actual efficient and unified command in face of a rag-tag army.
Either we consider him having some military skills and counted on that exact kind of situation (it's not like he didn't had experiance of it at this point), or we consider Henry V to be slightly less affected by the stupidity epidemics.