The lack of French subsidy will of course be more relevant in the next phases of the war, but if Louis XIII was to break his neck somehow, Gaston (ugh) would accede to the throne. Since he was pretty much inept and still very young, there would be a great deal of infighting, especially since his mother would stick her oar in – AGAIN. Richelieu had just broken his long association with her since her patronage had got him where he wanted, the Chief Minister of France and she was frankly a load. France might thus be too inward-looking (and descending into civil war) to be spending any amount of money on the usual 'screw with the Habsburgs' line in the budget.