The last thing you do ( closing..), most always, affects the next thing to happen.   I'd say the closing did the trick, not the breath of fresh air..

 The choke system uses temperature, spring tension and vacuum to operate.  Since the engine requires a fuel-air ratio of around 14:1 to operate normally, starting cold requires a much denser charge.  There's no way to vaporize fuel when cold, so the choke facilitates this denser mixture by closing off the air and drawing liquid fuel into the manifold. The proper way to start a car in the 50-60s, was to press the gas pedal to the floor to set the choke, add another short pedal stroke to inject some more fuel into the throat of the carb and turn the key.   If you look down, into the manifold, there's a casting feature, on the floor, which looks like a waffle iron grid.  It is there to prevent liquid fuel from running into the cylinders.   As soon as the engine starts, the manifold vacuum pulls the choke open further to lean out the mixture. This is accomplished through manifold vacuum, acting on the piston inside the choke housing.   As the engine warms up, the temperature from the stove under the choke tube is drawn into the choke housing and the bi-metal spring expands, relieving tension on the choke flap.
  There are cams in the inkage to adjust fast idle at cold temperatures and normal idle at warm temps.  The choke spring is what moves the linkage over the steps on the fast idle cam.
 All these functions, working correctly, depend on your engine condition.  Vacuum leaks can occur from out of round holes caused by the carburator throttle shaft wearing against the carb body, leaking hoses or gaskets, spark plug condition, engine wear, etc.  The fuel in use, today,  is functionally designed for closed fuel injection systems, where there is no atmospheric vent to allow the fuel to vapor off in high temperature conditions.  Having an exposed fuel line, under the hood will be more suseptible to the engine heat causing vapor lock.  (The vapor lock problem can be countered by having an electric fuel pump, managed by a manual switch, under the dash.)  The specific gravity of todays fuel formulas is lighter than the old and will sometimes cause your carb float to allow a higher than required fuel level, causing an over rich or stumbling condition.   The alcohol content in fuels can be detrimental to old rubber compounds and also act as a system cleaner, dissolving hardened contaminants, into your system and forcing them thru the carb, resulting in a rough running engine.  The rubber problem is cleared by using newer fuel injection hoses and modern fuel pumps, either electric or 'kitted' with newer components. 
So, there's a lot of 'sausage' being made, with all the variances in conditions of todays technology meeting the mechanicals of yesteryear...