How the Third Republic fell is a different matter from why the Third Republic fell. The majority of the French supported the Popular Front, but the Front was fissiparous. The reactionary opposition, was uncompromising and willing to unleash stormtrooper mobs in the streets, and the battles in the streets deligitimized the government, as unable to maintain order. Cabinets in crisis formed and dissolved frequently, preventing any single policy from maturing.
That is the 'how' of the matter, but the 'why' of the matter is that high unemployment created a crisis and unemployment furnished the men for the mobs. Waiting far too long, France's adherence to the gold standard bankrupted her before she finally climbed down. In this state of bankruptcy, the government could do little to alleviate the misery of the unemployed.
In Germany, Hitler simply conscripted the unemployed and set them to work. In Britain, the English went off the gold standard early and mastered their finances well enough to maintain trade and provide a dole. In America millions were put to work building schools, hospitals, roads- all of the basic infrastructure that would pay off in spades after WW II.
But today, our memories have faded, and very few liberals can explain in clear and moving terms why we should pay taxes, and what we should be paying for. We find ourselves, like the Third Republic, unable to believe that we can provide social welfare, or relieve unemployment, and have, in short, bankrupted ourselves mentally while our finances, in real terms, are not that bad.
This confusion only gets worse when it is proposed to fight unemployment by building a freeway. With the greatest change in the history of humanity hanging over us, our responses need to be coherent. Above all, they must be funded, but there are many ways to do that- if the investment is a sound one.