There is a good summary regarding the reasons for the fall of France here
http://en.wikipedia.org/wiki/Battle_of_France
An extract relevant to the last few posts is copied below
Outdated tactics. It is often assumed that there was a neglect of tank warfare by the French, exemplified by the rejection of Colonel
Charles de Gaulle's tank warfare tactics by the French high command. The French had built a larger number of modern tanks than the Germans and these were on average better armed and armoured. Also it is untrue that they were divided among the infantry in "penny-packets" or even individually assigned to infantry units as support vehicles; even the independent tank battalions were combined in
Groupements and allocated at army level. However, the French suffered from an inflexible division in infantry tanks and cavalry tanks: ironically the former were insufficiently trained to cooperate with the infantry and so couldn't execute modern combined arms tactics. In theory the operational doctrine of both armies was based on partly mechanized maneuver warfare; in practice the French shied away from it, while the best German field commanders were so bold as to let it develop into pure Blitzkrieg if the situation allowed.