I see you haven't gotten an answer but i can give you an idea.
The pressure we normally experience keeps pressure on our molecules sorta. So when you lower the pressure like the vacuum then the same amount of energy to move around further due to less pressure on it. Since state changes are really just how far away and loose a molecules structure is they can use less energy to move around and go into a gas state instead of liquid. This applies to gas to, the pressure the gas is changes its ability to move. The less pressure the bigger the gass expands or stretches out with the equivalent energy it has. It doesn't need to change state since its already a gas it just gets excited more cause it can move around and stretch its legs more cause its under less pressure.
This is a very basic explanation that is somewhat flawed. But thats also why lowering the pressure can cause water to boil, its starts to stretch (vapor pressure vs pressure exerted) and begins to transform (the vapor pressure equals or exceeds the ambient pressure and begins to form 'bubbles' or less dense areas that are less dense then liquid and raises up eventually forming with the rest of the substance into a gas) to a gas just like increasing the heat increases the energy lowering the pressure allows more movement with same energy heat gives energy to allow more movement.
The same process happens from solid -> liquid -> gas and doesn't stop, the more energy or less pressure the more the gas can expand. Those the CO2 is expanding and pushing itself out side the liquid causing a forming reaction with the liquid trapping the gas raising out, the tension of that liquid holds onto more and more bubbles of air creating that foaming effect as the gas expands and pushes the liquid and other gas forcing itself out.
Imagine having a bunch or marble size balloons in a cup with water, if you blow up the balloons at the same time they force the liquid and other balloons out. You have the above reaction.
God I am terrible at chemistry I really hope this makes sense!